From 68568abe3a4ed99f5456cf8b1b8c39b0987a0f9c Mon Sep 17 00:00:00 2001
From: Fedor <fedor@mail.ru>
Date: Sat, 19 Apr 2025 19:16:30 +0300
Subject: [PATCH] 68.14.8 - testing

---
 .../keyboard_shortcuts/test_browser_window.py |    1 -
 .../firefox-ui/tests/functional/manifest.ini  |    1 -
 .../functional/private_browsing/manifest.ini  |    4 -
 .../test_about_private_browsing.py            |   73 -
 .../tests/puppeteer/test_toolbars.py          |   96 +-
 .../tests/puppeteer/test_windows.py           |    2 +-
 testing/marionette/capture.js                 |   63 +-
 .../chrome/{test.xul => test.xhtml}           |   12 +-
 testing/marionette/chrome/test2.xhtml         |   20 +
 testing/marionette/chrome/test2.xul           |   19 -
 .../chrome/test_anonymous_content.xul         |   37 -
 .../{test_dialog.xul => test_dialog.xhtml}    |    7 +-
 ...ed_iframe.xul => test_nested_iframe.xhtml} |    2 +-
 .../client/docs/advanced/findelement.rst      |   39 -
 .../marionette/client/marionette_driver/by.py |    2 -
 .../client/marionette_driver/marionette.py    |   28 +-
 testing/marionette/components/marionette.js   |    5 +-
 testing/marionette/doc/internals/element.rst  |    4 -
 testing/marionette/driver.js                  |   78 +-
 testing/marionette/element.js                 |   72 +-
 .../harness/marionette_harness/__init__.py    |    1 -
 .../marionette_test/__init__.py               |    1 -
 .../marionette_test/decorators.py             |   15 -
 .../tests/unit/test_anonymous_content.py      |   87 -
 .../tests/unit/test_checkbox_chrome.py        |    2 +-
 .../tests/unit/test_click.py                  |    2 -
 .../tests/unit/test_click_chrome.py           |    2 +-
 .../tests/unit/test_element_state_chrome.py   |    2 +-
 .../tests/unit/test_elementsize_chrome.py     |    2 +-
 .../tests/unit/test_execute_sandboxes.py      |    3 +-
 .../tests/unit/test_execute_script.py         |   11 +-
 .../tests/unit/test_findelement_chrome.py     |    8 +-
 .../tests/unit/test_get_current_url_chrome.py |    5 +-
 .../tests/unit/test_marionette.py             |    4 +-
 .../tests/unit/test_mouse_action.py           |    4 +-
 .../tests/unit/test_navigation.py             |   13 +-
 .../tests/unit/test_pagesource_chrome.py      |    4 +-
 .../tests/unit/test_prefs.py                  |   14 -
 .../tests/unit/test_screen_orientation.py     |    6 -
 .../tests/unit/test_screenshot.py             |   74 +-
 .../tests/unit/test_switch_frame_chrome.py    |   20 +-
 .../tests/unit/test_switch_window_content.py  |    2 -
 .../tests/unit/test_timeouts.py               |    3 +-
 .../tests/unit/test_title_chrome.py           |    2 +-
 .../tests/unit/test_typing.py                 |    8 +-
 .../tests/unit/test_window_close_chrome.py    |    2 +-
 .../tests/unit/test_window_close_content.py   |    9 +-
 .../tests/unit/test_window_handles_chrome.py  |   12 +-
 .../tests/unit/test_window_handles_content.py |    7 +-
 .../tests/unit/test_window_management.py      |    6 +-
 .../tests/unit/test_window_status_content.py  |    6 +-
 .../tests/unit/test_window_type_chrome.py     |    2 +-
 .../tests/unit/unit-tests.ini                 |   34 +-
 testing/marionette/interaction.js             |    1 -
 testing/marionette/jar.mn                     |   11 +-
 testing/marionette/listener.js                |   45 +-
 testing/marionette/modal.js                   |    2 +-
 .../firefox/docs/ui/browser/tabbar.rst        |    6 -
 .../ui/browser/notifications.py               |    3 +-
 .../firefox_puppeteer/ui/browser/tabbar.py    |   61 +-
 .../firefox_puppeteer/ui/browser/toolbars.py  |  155 +-
 .../firefox_puppeteer/ui/browser/window.py    |    1 -
 .../ui/update_wizard/wizard.py                |    2 +-
 testing/marionette/reftest.js                 |    3 +-
 .../marionette/{reftest.xul => reftest.xhtml} |    0
 .../BrowserTestUtils/BrowserTestUtils.jsm     |   12 +-
 .../baselinecoverage/chrome/chrome.ini        |    2 +-
 ...verage.xul => test_baselinecoverage.xhtml} |    0
 ...wser-harness.xul => browser-harness.xhtml} |    2 +-
 testing/mochitest/browser-test.js             |  289 +--
 testing/mochitest/chrome/chrome.ini           |   18 +-
 ...tFile.xul => test_chromeGetTestFile.xhtml} |    8 +-
 .../{test_sample.xul => test_sample.xhtml}    |    0
 ...tUtils.xul => test_sanityEventUtils.xhtml} |   18 -
 ...ception.xul => test_sanityException.xhtml} |    0
 ...ption2.xul => test_sanityException2.xhtml} |    0
 ...Manifest.xul => test_sanityManifest.xhtml} |    0
 ...st_pf.xul => test_sanityManifest_pf.xhtml} |    0
 ...t_tasks_skip.xul => test_tasks_skip.xhtml} |    0
 ...s_skipall.xul => test_tasks_skipall.xhtml} |    0
 .../mochitest/{harness.xul => harness.xhtml}  |    0
 testing/mochitest/leaks.py                    |    2 +-
 testing/mochitest/mochitest_options.py        |    6 -
 testing/mochitest/moz.build                   |    8 +-
 testing/mochitest/redirect.html               |    2 +-
 .../test_SpecialPowersExtension.html          |   12 +-
 .../mochitest/tests/SimpleTest/EventUtils.js  | 1674 +++++++++++------
 .../tests/SimpleTest/ExtensionTestUtils.js    |   16 +-
 .../mochitest/tests/SimpleTest/SimpleTest.js  |    4 +-
 testing/mochitest/tests/browser/dummy.html    |    2 +-
 testing/mozbase/mozrunner/mozrunner/utils.py  |    3 +
 .../configs/unittests/linux_unittest.py       |    1 -
 .../configs/unittests/mac_unittest.py         |    1 -
 .../configs/unittests/win_unittest.py         |    1 -
 .../mozilla/testing/codecoverage.py           |    4 +-
 testing/profiles/common/user.js               |    1 -
 testing/profiles/raptor-android/user.js       |    4 +
 testing/talos/talos/pageloader/api.js         |   10 +-
 .../{pageloader.xul => pageloader.xhtml}      |    0
 .../sessionrestore/profile/sessionstore.js    |    3 -
 testing/talos/talos/talos-powers/api.js       |   17 +-
 .../talos/talos/tests/devtools/addon/api.js   |    2 +-
 .../tart/addon/content/tab-min-width-1px.css  |    2 +-
 .../talos/tests/tart/addon/content/tart.js    |   17 +-
 testing/talos/talos/tests/twinopen/api.js     |    2 +-
 .../talos/talos/xtalos/xperf_whitelist.json   |    2 +-
 .../drawFocusIfNeeded_001.html.ini            |    7 -
 .../drawFocusIfNeeded_004.html.ini            |    7 -
 .../drawFocusIfNeeded_005.html.ini            |    7 -
 .../meta/css/CSS2/bidi-text/bidi-001.xht.ini  |    3 +-
 .../meta/css/CSS2/bidi-text/bidi-002.xht.ini  |    1 +
 .../CSS2/bidi-text/bidi-box-model-003.xht.ini |    3 +
 .../meta/css/css-flexbox/__dir__.ini          |    1 +
 .../table-grid-item-dynamic-004.html.ini      |    4 +-
 .../css-pseudo/selection-input-011.html.ini   |    2 +
 .../selection-intercharacter-011.html.ini     |    2 +
 .../selection-intercharacter-012.html.ini     |    2 +
 .../selection-textarea-011.html.ini           |    5 +
 .../boundary-shaping-010.html.ini             |    5 -
 .../css-text/shaping/shaping_lig-000.html.ini |    4 -
 .../meta/css/selectors/__dir__.ini            |    3 +-
 .../css/selectors/focus-visible-003.html.ini  |    6 +
 .../css/selectors/focus-visible-005.html.ini  |    3 +-
 .../drawFocusIfNeeded_001.html.ini            |    5 -
 .../drawFocusIfNeeded_004.html.ini            |    5 -
 .../drawFocusIfNeeded_005.html.ini            |    5 -
 .../the-bdo-element/bdo-child.html.ini        |    3 +
 .../the-bdo-element/bidi-001.html.ini         |    3 +
 .../buffered-flag.window.js.ini               |    4 +
 .../longtask-timing/containerTypes.html.ini   |   13 +
 .../longtask-timing/idlharness.window.js.ini  |    3 -
 .../long-microtask.window.js.ini              |    4 +
 .../longtask-attributes.html.ini              |    3 -
 ...ngtask-in-childiframe-crossorigin.html.ini |    6 -
 .../longtask-in-childiframe.html.ini          |    3 -
 .../longtask-in-externalscript.html.ini       |    3 -
 .../longtask-in-parentiframe.html.ini         |    3 -
 .../longtask-timing/longtask-in-raf.html.ini  |    3 -
 ...ask-in-sibling-iframe-crossorigin.html.ini |    6 -
 .../longtask-in-sibling-iframe.html.ini       |    6 -
 .../supported-longtask-types.window.js.ini    |    3 +
 .../direction/direction-008.html.ini          |    3 +
 .../direction/direction-009.html.ini          |    4 +
 .../fractions/frac-linethickness-001.html.ini |    2 +-
 .../frac-parameters-gap-001.html.ini          |    5 +
 .../frac-parameters-gap-002.html.ini          |    5 +
 .../frac-parameters-gap-003.html.ini          |    5 +
 .../frac-parameters-gap-004.html.ini          |    5 +
 .../frac-parameters-gap-005.html.ini          |    5 +
 .../frac-parameters-gap-006.html.ini          |    5 +
 .../operators/mo-movablelimits.html.ini       |    2 +
 .../attribute-mapping-001.html.ini            |  196 ++
 .../attribute-mapping-002.html.ini            |  288 +++
 .../relations/css-styling/color-001.html.ini  |    3 +
 .../relations/css-styling/color-002.html.ini  |    3 +
 .../relations/css-styling/color-003.html.ini  |    3 +
 .../relations/css-styling/color-004.html.ini  |    5 +
 .../relations/css-styling/color-1.html.ini    |    5 -
 .../relations/css-styling/lengths-1.html.ini  |    2 +-
 .../relations/css-styling/lengths-2.html.ini  |    8 +
 .../mathsize-attribute-css-keywords.html.ini  |    2 +
 .../mathsize-attribute-legacy-values.html.ini |    2 +
 .../padding-border-margin/border-001.html.ini |   18 +
 .../padding-border-margin/border-002.html.ini |  147 ++
 .../padding-border-margin/margin-001.html.ini |   18 +
 .../padding-border-margin/margin-002.html.ini |  219 +++
 .../padding-001.html.ini                      |   18 +
 .../padding-002.html.ini                      |  147 ++
 .../css-styling/width-height-001.html.ini     |    6 +
 .../writing-mode/writing-mode-001.html.ini    |   19 +
 .../writing-mode/writing-mode-002.html.ini    |  372 ++++
 .../meta/paint-timing/__dir__.ini             |    0
 .../fcp-only/fcp-background-size.html.ini     |    4 -
 .../fcp-only/fcp-bg-image-set.html.ini        |    3 +-
 .../fcp-only/fcp-bg-image-two-steps.html.ini  |    4 -
 .../fcp-only/fcp-canvas-context.html.ini      |    4 -
 .../fcp-only/fcp-gradient.html.ini            |    4 -
 ...cp-invisible-3d-rotate-descendant.html.ini |    4 -
 .../fcp-only/fcp-invisible-3d-rotate.html.ini |    4 -
 .../fcp-invisible-scale-transition.html.ini   |    4 -
 .../fcp-only/fcp-invisible-scale.html.ini     |    4 -
 .../fcp-only/fcp-invisible-text.html.ini      |    4 -
 .../fcp-only/fcp-opacity-descendant.html.ini  |    4 -
 .../fcp-only/fcp-opacity.html.ini             |    4 -
 .../fcp-out-of-bounds-translate.html.ini      |    4 -
 .../fcp-only/fcp-out-of-bounds.html.ini       |    4 -
 .../fcp-pseudo-element-display.html.ini       |    4 -
 .../fcp-pseudo-element-image.html.ini         |    4 -
 .../fcp-pseudo-element-opacity.html.ini       |    4 -
 .../fcp-only/fcp-pseudo-element-text.html.ini |    4 -
 .../fcp-pseudo-element-visibility.html.ini    |    4 -
 .../paint-timing/fcp-only/fcp-svg.html.ini    |    4 -
 .../fcp-only/fcp-text-input.html.ini          |    4 +
 .../fcp-only/fcp-video-frame.html.ini         |    3 +-
 .../fcp-only/fcp-video-poster.html.ini        |    4 -
 .../fcp-only/fcp-whitespace.html.ini          |    4 -
 .../first-contentful-canvas-none.html.ini     |    3 +
 .../paint-timing/idlharness.window.js.ini     |   31 -
 .../meta/paint-timing/input-text.html.ini     |    4 -
 .../replaced-content-image.html.ini           |    4 +-
 .../supported-paint-type.window.js.ini        |    4 -
 .../{ => with-first-paint}/basetest.html.ini  |    2 +-
 .../border-image.html.ini                     |    4 +-
 .../buffered-flag.window.js.ini               |    5 +
 .../child-painting-first-image.html.ini       |    2 +-
 .../first-contentful-bg-image.html.ini        |    2 +-
 .../first-contentful-canvas-webgl2.html.ini   |    3 +
 .../first-contentful-canvas.html.ini          |    2 +-
 .../first-contentful-image.html.ini           |    3 +-
 .../first-contentful-paint.html.ini           |    2 +-
 .../first-contentful-svg.html.ini             |    2 +-
 .../first-image-child.html.ini                |    2 +-
 .../first-paint-bg-color.html.ini             |    2 +-
 .../first-paint-only.html.ini                 |    2 +-
 .../mask-image.html.ini                       |    4 +-
 .../paint-visited.html.ini                    |    2 +-
 .../sibling-painting-first-image.html.ini     |    2 +-
 .../case-sensitivity.any.js.ini               |    7 +
 ...sconnect-removes-observed-types.any.js.ini |    8 +
 .../resource-timing/buffered-flag.any.js.ini  |    7 +
 .../meta/user-timing/idlharness.any.js.ini    |   11 +
 .../dynamic-isize-change-001-ref.html         |   37 +
 .../css-flexbox/dynamic-isize-change-001.html |   49 +
 .../css-flexbox/dynamic-isize-change-002.html |   40 +
 .../css-flexbox/dynamic-isize-change-003.html |   43 +
 .../css-flexbox/dynamic-isize-change-004.html |   42 +
 ...ith-percentage-width-in-flex-item-ref.html |   64 +
 ...ut-with-percentage-width-in-flex-item.html |   69 +
 .../css/css-flexbox/flex-basis-011-ref.html   |   21 +
 .../tests/css/css-flexbox/flex-basis-011.html |   24 +
 .../tests/css/css-flexbox/flex-basis-012.html |    9 +
 .../flexbox-baseline-nested-001-ref.html      |   26 +
 .../flexbox-baseline-nested-001.html          |   35 +
 ...grid-with-content-dynamic-display-001.html |   50 +
 ...grid-with-content-dynamic-display-002.html |   50 +
 .../nested-grid-item-block-size-001-ref.html  |   27 +
 .../nested-grid-item-block-size-001.html      |   37 +
 .../css/css-grid/support/colors-8x16.png      |  Bin 0 -> 92 bytes
 .../overflow-empty-child-box.html             |   59 +
 .../selection-contenteditable-011-ref.html    |   21 +
 .../reference/selection-input-011-ref.html    |   24 +
 .../selection-intercharacter-011-ref.html     |   26 +
 .../selection-intercharacter-012-ref.html     |   26 +
 .../reference/selection-textarea-011-ref.html |   27 +
 .../selection-contenteditable-011.html        |   45 +
 .../css/css-pseudo/selection-input-011.html   |   43 +
 .../selection-intercharacter-011.html         |   49 +
 .../selection-intercharacter-012.html         |   49 +
 .../css-pseudo/selection-textarea-011.html    |   46 +
 ...003-manual.html => focus-visible-003.html} |   19 +-
 .../selectors/focus-visible-004-manual.html   |    9 +-
 .../tests/element-timing/buffered-flag.html   |   42 +
 ...cus_drawFocusIfNeeded_AAPI_001-manual.html |    0
 .../drawFocusIfNeeded_001.html                |    0
 .../drawFocusIfNeeded_002.html                |    0
 .../drawFocusIfNeeded_003.html                |    0
 .../drawFocusIfNeeded_004.html                |    0
 .../drawFocusIfNeeded_005.html                |    0
 .../tests/interfaces/user-timing.idl          |   30 +-
 .../longtask-timing/buffered-flag.window.js   |   26 +
 .../tests/longtask-timing/containerTypes.html |   64 +
 .../longtask-timing/long-microtask.window.js  |   26 +
 .../longtask-timing/longtask-attributes.html  |    6 +-
 .../longtask-in-childiframe-crossorigin.html  |    6 +-
 .../longtask-in-childiframe.html              |    6 +-
 .../longtask-in-externalscript.html           |    6 +-
 .../longtask-in-parentiframe.html             |    6 +-
 .../longtask-timing/longtask-in-raf.html      |    6 +-
 ...ongtask-in-sibling-iframe-crossorigin.html |    6 +-
 .../longtask-in-sibling-iframe.html           |    6 +-
 .../longtask-timing/longtask-tojson.html      |    7 +-
 .../subframe-observing-longtask.html          |    1 +
 .../longtask-in-new-window.html               |    5 +-
 .../supported-longtask-types.window.js        |   31 +-
 .../direction/direction-006-ref.html          |   74 +
 .../direction/direction-006.html              |   79 +
 .../direction/direction-007-ref.html          |   42 +
 .../direction/direction-007.html              |   50 +
 .../direction/direction-008-ref.html          |   27 +
 .../direction/direction-008.html              |   33 +
 .../direction/direction-009-ref.html          |   21 +
 .../direction/direction-009.html              |   27 +
 .../direction/direction-010-ref.html          |   44 +
 .../direction/direction-010.html              |   51 +
 .../fractions/frac-linethickness-002-ref.html |    4 +-
 .../fractions/frac-linethickness-002.html     |    3 +-
 .../css-styling/attribute-mapping-001.html    |   85 +
 .../css-styling/attribute-mapping-002.html    |   59 +
 .../relations/css-styling/lengths-2-ref.html  |   14 -
 .../relations/css-styling/lengths-2.html      |  343 ++--
 .../relations/css-styling/lengths-3.html      |  159 --
 .../mathsize-attribute-css-keywords-ref.html  |   22 +
 .../mathsize-attribute-css-keywords.html      |   26 +
 .../mathsize-attribute-legacy-values-ref.html |   16 +
 .../mathsize-attribute-legacy-values.html     |   20 +
 .../css-styling/mathvariant-bold-fraktur.html |    4 +-
 .../css-styling/mathvariant-bold-italic.html  |    4 +-
 .../mathvariant-bold-sans-serif.html          |    4 +-
 .../css-styling/mathvariant-bold-script.html  |    4 +-
 .../css-styling/mathvariant-bold.html         |    4 +-
 .../mathvariant-double-struck.html            |    4 +-
 .../css-styling/mathvariant-fraktur.html      |    4 +-
 .../css-styling/mathvariant-initial.html      |    4 +-
 .../css-styling/mathvariant-italic.html       |    4 +-
 .../css-styling/mathvariant-looped.html       |    4 +-
 .../css-styling/mathvariant-monospace.html    |    4 +-
 .../mathvariant-sans-serif-bold-italic.html   |    4 +-
 .../mathvariant-sans-serif-italic.html        |    4 +-
 .../css-styling/mathvariant-sans-serif.html   |    4 +-
 .../css-styling/mathvariant-script.html       |    4 +-
 .../css-styling/mathvariant-stretched.html    |    4 +-
 .../css-styling/mathvariant-tailed.html       |    4 +-
 .../padding-border-margin/border-001.html     |  104 +
 .../padding-border-margin/border-002.html     |   51 +
 .../padding-border-margin/helper.js           |   79 +
 .../padding-border-margin/margin-001.html     |  104 +
 .../padding-border-margin/margin-002.html     |   51 +
 .../padding-border-margin/padding-001.html    |  104 +
 .../padding-border-margin/padding-002.html    |   51 +
 .../padding-border-margin/padding-003.html    |   39 +
 .../relations/css-styling/visibility-1.html   |    6 +-
 .../writing-mode/writing-mode-001.html        |  121 ++
 .../mathml/relations/html5-tree/class-1.html  |    3 +-
 .../mathml/relations/html5-tree/class-2.html  |    3 +-
 .../html5-tree/color-attributes-1.html        |    3 +-
 .../relations/html5-tree/display-1.html       |    3 +-
 .../relations/html5-tree/dynamic-1.html       |    2 +-
 .../relations/html5-tree/href-click-1.html    |    3 +-
 .../relations/html5-tree/href-click-2.html    |    3 +-
 .../relations/html5-tree/href-click-3.html    |    3 +-
 .../html5-tree/integration-point-1.html       |    2 +-
 .../html5-tree/integration-point-2.html       |    2 +-
 .../html5-tree/integration-point-3.html       |    2 +-
 .../html5-tree/required-extensions-2.html     |    2 +-
 .../html5-tree/unique-identifier-1.html       |    2 +-
 .../html5-tree/unique-identifier-2.html       |    3 +-
 .../html5-tree/unique-identifier-3.html       |    3 +-
 .../text-and-math/use-typo-metrics-1.html     |    2 +-
 .../tests/mathml/support/layout-comparison.js |   86 +
 .../tests/mathml/support/mathml-fragments.js  |  151 ++
 .../mathml/tools/mathvariant-transforms.py    |    4 +-
 .../navigation-timing/buffered-flag.window.js |   16 +
 .../test_document_onload.html                 |   48 +
 .../tests/paint-timing/basetest.html          |    1 +
 .../paint-timing/buffered-flag.window.js      |   35 +
 .../child-painting-first-image.html           |    1 +
 .../fcp-only/fcp-canvas-context.html          |    6 +-
 .../fcp-ensure-update-the-rendering-step.html |   55 +
 .../paint-timing/fcp-only/fcp-gradient.html   |    5 +-
 .../paint-timing/fcp-only/fcp-text-input.html |   23 +
 .../fcp-only/fcp-typographic-pseudo.html      |   32 +
 .../fcp-only/fcp-video-frame.html             |    7 +-
 .../fcp-only/fcp-video-poster.html            |    6 +-
 .../paint-timing/fcp-only/fcp-with-rtl.html   |   30 +
 .../first-contentful-bg-image.html            |    1 +
 .../paint-timing/first-contentful-canvas.html |    1 +
 .../paint-timing/first-contentful-image.html  |    1 +
 .../paint-timing/first-contentful-paint.html  |    1 +
 .../paint-timing/first-contentful-svg.html    |    1 +
 .../tests/paint-timing/first-image-child.html |   19 +-
 .../paint-timing/first-paint-bg-color.html    |    1 +
 .../tests/paint-timing/first-paint-only.html  |    1 +
 .../tests/paint-timing/paint-visited.html     |    6 +-
 .../tests/paint-timing/resources/utils.js     |   46 +-
 .../sibling-painting-first-image.html         |    1 +
 .../supported-paint-type.window.js            |   35 +-
 .../buffered-flag-after-timeout.any.js        |   11 +
 .../buffered-flag-observer.any.js             |   15 +
 .../multiple-buffered-flag-observers.any.js   |   32 +
 .../observer-buffered-false.any.js            |   12 +
 ...o-disconnect-removes-observed-types.any.js |   19 +
 .../po-observe-repeated-type.any.js           |   17 +
 .../resource-timing/buffered-flag.any.js      |   18 +
 .../tests/user-timing/buffered-flag.any.js    |   27 +
 374 files changed, 6669 insertions(+), 2721 deletions(-)
 delete mode 100644 testing/firefox-ui/tests/functional/private_browsing/manifest.ini
 delete mode 100644 testing/firefox-ui/tests/functional/private_browsing/test_about_private_browsing.py
 rename testing/marionette/chrome/{test.xul => test.xhtml} (68%)
 create mode 100644 testing/marionette/chrome/test2.xhtml
 delete mode 100644 testing/marionette/chrome/test2.xul
 delete mode 100644 testing/marionette/chrome/test_anonymous_content.xul
 rename testing/marionette/chrome/{test_dialog.xul => test_dialog.xhtml} (84%)
 rename testing/marionette/chrome/{test_nested_iframe.xul => test_nested_iframe.xhtml} (81%)
 delete mode 100644 testing/marionette/harness/marionette_harness/tests/unit/test_anonymous_content.py
 rename testing/marionette/{reftest.xul => reftest.xhtml} (100%)
 rename testing/mochitest/baselinecoverage/chrome/{test_baselinecoverage.xul => test_baselinecoverage.xhtml} (100%)
 rename testing/mochitest/{browser-harness.xul => browser-harness.xhtml} (99%)
 rename testing/mochitest/chrome/{test_chromeGetTestFile.xul => test_chromeGetTestFile.xhtml} (93%)
 rename testing/mochitest/chrome/{test_sample.xul => test_sample.xhtml} (100%)
 rename testing/mochitest/chrome/{test_sanityEventUtils.xul => test_sanityEventUtils.xhtml} (85%)
 rename testing/mochitest/chrome/{test_sanityException.xul => test_sanityException.xhtml} (100%)
 rename testing/mochitest/chrome/{test_sanityException2.xul => test_sanityException2.xhtml} (100%)
 rename testing/mochitest/chrome/{test_sanityManifest.xul => test_sanityManifest.xhtml} (100%)
 rename testing/mochitest/chrome/{test_sanityManifest_pf.xul => test_sanityManifest_pf.xhtml} (100%)
 rename testing/mochitest/chrome/{test_tasks_skip.xul => test_tasks_skip.xhtml} (100%)
 rename testing/mochitest/chrome/{test_tasks_skipall.xul => test_tasks_skipall.xhtml} (100%)
 rename testing/mochitest/{harness.xul => harness.xhtml} (100%)
 rename testing/talos/talos/pageloader/chrome/{pageloader.xul => pageloader.xhtml} (100%)
 delete mode 100644 testing/web-platform/meta/2dcontext/drawing-paths-to-the-canvas/drawFocusIfNeeded_001.html.ini
 delete mode 100644 testing/web-platform/meta/2dcontext/drawing-paths-to-the-canvas/drawFocusIfNeeded_004.html.ini
 delete mode 100644 testing/web-platform/meta/2dcontext/drawing-paths-to-the-canvas/drawFocusIfNeeded_005.html.ini
 create mode 100644 testing/web-platform/meta/css/CSS2/bidi-text/bidi-box-model-003.xht.ini
 create mode 100644 testing/web-platform/meta/css/css-flexbox/__dir__.ini
 create mode 100644 testing/web-platform/meta/css/css-pseudo/selection-input-011.html.ini
 create mode 100644 testing/web-platform/meta/css/css-pseudo/selection-intercharacter-011.html.ini
 create mode 100644 testing/web-platform/meta/css/css-pseudo/selection-intercharacter-012.html.ini
 create mode 100644 testing/web-platform/meta/css/css-pseudo/selection-textarea-011.html.ini
 delete mode 100644 testing/web-platform/meta/css/css-text/boundary-shaping/boundary-shaping-010.html.ini
 delete mode 100644 testing/web-platform/meta/css/css-text/shaping/shaping_lig-000.html.ini
 create mode 100644 testing/web-platform/meta/css/selectors/focus-visible-003.html.ini
 delete mode 100644 testing/web-platform/meta/html/canvas/element/drawing-paths-to-the-canvas/drawFocusIfNeeded_001.html.ini
 delete mode 100644 testing/web-platform/meta/html/canvas/element/drawing-paths-to-the-canvas/drawFocusIfNeeded_004.html.ini
 delete mode 100644 testing/web-platform/meta/html/canvas/element/drawing-paths-to-the-canvas/drawFocusIfNeeded_005.html.ini
 create mode 100644 testing/web-platform/meta/html/semantics/text-level-semantics/the-bdo-element/bdo-child.html.ini
 create mode 100644 testing/web-platform/meta/html/semantics/text-level-semantics/the-bdo-element/bidi-001.html.ini
 create mode 100644 testing/web-platform/meta/longtask-timing/buffered-flag.window.js.ini
 create mode 100644 testing/web-platform/meta/longtask-timing/containerTypes.html.ini
 create mode 100644 testing/web-platform/meta/longtask-timing/long-microtask.window.js.ini
 create mode 100644 testing/web-platform/meta/mathml/presentation-markup/direction/direction-008.html.ini
 create mode 100644 testing/web-platform/meta/mathml/presentation-markup/direction/direction-009.html.ini
 create mode 100644 testing/web-platform/meta/mathml/presentation-markup/fractions/frac-parameters-gap-001.html.ini
 create mode 100644 testing/web-platform/meta/mathml/presentation-markup/fractions/frac-parameters-gap-002.html.ini
 create mode 100644 testing/web-platform/meta/mathml/presentation-markup/fractions/frac-parameters-gap-003.html.ini
 create mode 100644 testing/web-platform/meta/mathml/presentation-markup/fractions/frac-parameters-gap-004.html.ini
 create mode 100644 testing/web-platform/meta/mathml/presentation-markup/fractions/frac-parameters-gap-005.html.ini
 create mode 100644 testing/web-platform/meta/mathml/presentation-markup/fractions/frac-parameters-gap-006.html.ini
 create mode 100644 testing/web-platform/meta/mathml/presentation-markup/operators/mo-movablelimits.html.ini
 create mode 100644 testing/web-platform/meta/mathml/relations/css-styling/attribute-mapping-001.html.ini
 create mode 100644 testing/web-platform/meta/mathml/relations/css-styling/attribute-mapping-002.html.ini
 create mode 100644 testing/web-platform/meta/mathml/relations/css-styling/color-001.html.ini
 create mode 100644 testing/web-platform/meta/mathml/relations/css-styling/color-002.html.ini
 create mode 100644 testing/web-platform/meta/mathml/relations/css-styling/color-003.html.ini
 create mode 100644 testing/web-platform/meta/mathml/relations/css-styling/color-004.html.ini
 delete mode 100644 testing/web-platform/meta/mathml/relations/css-styling/color-1.html.ini
 create mode 100644 testing/web-platform/meta/mathml/relations/css-styling/lengths-2.html.ini
 create mode 100644 testing/web-platform/meta/mathml/relations/css-styling/mathsize-attribute-css-keywords.html.ini
 create mode 100644 testing/web-platform/meta/mathml/relations/css-styling/mathsize-attribute-legacy-values.html.ini
 create mode 100644 testing/web-platform/meta/mathml/relations/css-styling/padding-border-margin/border-001.html.ini
 create mode 100644 testing/web-platform/meta/mathml/relations/css-styling/padding-border-margin/border-002.html.ini
 create mode 100644 testing/web-platform/meta/mathml/relations/css-styling/padding-border-margin/margin-001.html.ini
 create mode 100644 testing/web-platform/meta/mathml/relations/css-styling/padding-border-margin/margin-002.html.ini
 create mode 100644 testing/web-platform/meta/mathml/relations/css-styling/padding-border-margin/padding-001.html.ini
 create mode 100644 testing/web-platform/meta/mathml/relations/css-styling/padding-border-margin/padding-002.html.ini
 create mode 100644 testing/web-platform/meta/mathml/relations/css-styling/width-height-001.html.ini
 create mode 100644 testing/web-platform/meta/mathml/relations/css-styling/writing-mode/writing-mode-001.html.ini
 create mode 100644 testing/web-platform/meta/mathml/relations/css-styling/writing-mode/writing-mode-002.html.ini
 delete mode 100644 testing/web-platform/meta/paint-timing/__dir__.ini
 delete mode 100644 testing/web-platform/meta/paint-timing/fcp-only/fcp-background-size.html.ini
 delete mode 100644 testing/web-platform/meta/paint-timing/fcp-only/fcp-bg-image-two-steps.html.ini
 delete mode 100644 testing/web-platform/meta/paint-timing/fcp-only/fcp-canvas-context.html.ini
 delete mode 100644 testing/web-platform/meta/paint-timing/fcp-only/fcp-gradient.html.ini
 delete mode 100644 testing/web-platform/meta/paint-timing/fcp-only/fcp-invisible-3d-rotate-descendant.html.ini
 delete mode 100644 testing/web-platform/meta/paint-timing/fcp-only/fcp-invisible-3d-rotate.html.ini
 delete mode 100644 testing/web-platform/meta/paint-timing/fcp-only/fcp-invisible-scale-transition.html.ini
 delete mode 100644 testing/web-platform/meta/paint-timing/fcp-only/fcp-invisible-scale.html.ini
 delete mode 100644 testing/web-platform/meta/paint-timing/fcp-only/fcp-invisible-text.html.ini
 delete mode 100644 testing/web-platform/meta/paint-timing/fcp-only/fcp-opacity-descendant.html.ini
 delete mode 100644 testing/web-platform/meta/paint-timing/fcp-only/fcp-opacity.html.ini
 delete mode 100644 testing/web-platform/meta/paint-timing/fcp-only/fcp-out-of-bounds-translate.html.ini
 delete mode 100644 testing/web-platform/meta/paint-timing/fcp-only/fcp-out-of-bounds.html.ini
 delete mode 100644 testing/web-platform/meta/paint-timing/fcp-only/fcp-pseudo-element-display.html.ini
 delete mode 100644 testing/web-platform/meta/paint-timing/fcp-only/fcp-pseudo-element-image.html.ini
 delete mode 100644 testing/web-platform/meta/paint-timing/fcp-only/fcp-pseudo-element-opacity.html.ini
 delete mode 100644 testing/web-platform/meta/paint-timing/fcp-only/fcp-pseudo-element-text.html.ini
 delete mode 100644 testing/web-platform/meta/paint-timing/fcp-only/fcp-pseudo-element-visibility.html.ini
 delete mode 100644 testing/web-platform/meta/paint-timing/fcp-only/fcp-svg.html.ini
 create mode 100644 testing/web-platform/meta/paint-timing/fcp-only/fcp-text-input.html.ini
 delete mode 100644 testing/web-platform/meta/paint-timing/fcp-only/fcp-video-poster.html.ini
 delete mode 100644 testing/web-platform/meta/paint-timing/fcp-only/fcp-whitespace.html.ini
 create mode 100644 testing/web-platform/meta/paint-timing/first-contentful-canvas-none.html.ini
 delete mode 100644 testing/web-platform/meta/paint-timing/idlharness.window.js.ini
 delete mode 100644 testing/web-platform/meta/paint-timing/input-text.html.ini
 delete mode 100644 testing/web-platform/meta/paint-timing/supported-paint-type.window.js.ini
 rename testing/web-platform/meta/paint-timing/{ => with-first-paint}/basetest.html.ini (57%)
 rename testing/web-platform/meta/paint-timing/{ => with-first-paint}/border-image.html.ini (61%)
 create mode 100644 testing/web-platform/meta/paint-timing/with-first-paint/buffered-flag.window.js.ini
 rename testing/web-platform/meta/paint-timing/{ => with-first-paint}/child-painting-first-image.html.ini (67%)
 rename testing/web-platform/meta/paint-timing/{ => with-first-paint}/first-contentful-bg-image.html.ini (65%)
 create mode 100644 testing/web-platform/meta/paint-timing/with-first-paint/first-contentful-canvas-webgl2.html.ini
 rename testing/web-platform/meta/paint-timing/{ => with-first-paint}/first-contentful-canvas.html.ini (62%)
 rename testing/web-platform/meta/paint-timing/{ => with-first-paint}/first-contentful-image.html.ini (57%)
 rename testing/web-platform/meta/paint-timing/{ => with-first-paint}/first-contentful-paint.html.ini (69%)
 rename testing/web-platform/meta/paint-timing/{ => with-first-paint}/first-contentful-svg.html.ini (59%)
 rename testing/web-platform/meta/paint-timing/{ => with-first-paint}/first-image-child.html.ini (66%)
 rename testing/web-platform/meta/paint-timing/{ => with-first-paint}/first-paint-bg-color.html.ini (61%)
 rename testing/web-platform/meta/paint-timing/{ => with-first-paint}/first-paint-only.html.ini (65%)
 rename testing/web-platform/meta/paint-timing/{ => with-first-paint}/mask-image.html.ini (60%)
 rename testing/web-platform/meta/paint-timing/{ => with-first-paint}/paint-visited.html.ini (60%)
 rename testing/web-platform/meta/paint-timing/{ => with-first-paint}/sibling-painting-first-image.html.ini (65%)
 create mode 100644 testing/web-platform/meta/performance-timeline/case-sensitivity.any.js.ini
 create mode 100644 testing/web-platform/meta/performance-timeline/po-disconnect-removes-observed-types.any.js.ini
 create mode 100644 testing/web-platform/meta/resource-timing/buffered-flag.any.js.ini
 create mode 100644 testing/web-platform/tests/css/css-flexbox/dynamic-isize-change-001-ref.html
 create mode 100644 testing/web-platform/tests/css/css-flexbox/dynamic-isize-change-001.html
 create mode 100644 testing/web-platform/tests/css/css-flexbox/dynamic-isize-change-002.html
 create mode 100644 testing/web-platform/tests/css/css-flexbox/dynamic-isize-change-003.html
 create mode 100644 testing/web-platform/tests/css/css-flexbox/dynamic-isize-change-004.html
 create mode 100644 testing/web-platform/tests/css/css-flexbox/fixed-table-layout-with-percentage-width-in-flex-item-ref.html
 create mode 100644 testing/web-platform/tests/css/css-flexbox/fixed-table-layout-with-percentage-width-in-flex-item.html
 create mode 100644 testing/web-platform/tests/css/css-flexbox/flex-basis-011-ref.html
 create mode 100644 testing/web-platform/tests/css/css-flexbox/flex-basis-011.html
 create mode 100644 testing/web-platform/tests/css/css-flexbox/flex-basis-012.html
 create mode 100644 testing/web-platform/tests/css/css-flexbox/flexbox-baseline-nested-001-ref.html
 create mode 100644 testing/web-platform/tests/css/css-flexbox/flexbox-baseline-nested-001.html
 create mode 100644 testing/web-platform/tests/css/css-grid/grid-with-content-dynamic-display-001.html
 create mode 100644 testing/web-platform/tests/css/css-grid/grid-with-content-dynamic-display-002.html
 create mode 100644 testing/web-platform/tests/css/css-grid/nested-grid-item-block-size-001-ref.html
 create mode 100644 testing/web-platform/tests/css/css-grid/nested-grid-item-block-size-001.html
 create mode 100644 testing/web-platform/tests/css/css-grid/support/colors-8x16.png
 create mode 100644 testing/web-platform/tests/css/css-overflow/overflow-empty-child-box.html
 create mode 100644 testing/web-platform/tests/css/css-pseudo/reference/selection-contenteditable-011-ref.html
 create mode 100644 testing/web-platform/tests/css/css-pseudo/reference/selection-input-011-ref.html
 create mode 100644 testing/web-platform/tests/css/css-pseudo/reference/selection-intercharacter-011-ref.html
 create mode 100644 testing/web-platform/tests/css/css-pseudo/reference/selection-intercharacter-012-ref.html
 create mode 100644 testing/web-platform/tests/css/css-pseudo/reference/selection-textarea-011-ref.html
 create mode 100644 testing/web-platform/tests/css/css-pseudo/selection-contenteditable-011.html
 create mode 100644 testing/web-platform/tests/css/css-pseudo/selection-input-011.html
 create mode 100644 testing/web-platform/tests/css/css-pseudo/selection-intercharacter-011.html
 create mode 100644 testing/web-platform/tests/css/css-pseudo/selection-intercharacter-012.html
 create mode 100644 testing/web-platform/tests/css/css-pseudo/selection-textarea-011.html
 rename testing/web-platform/tests/css/selectors/{focus-visible-003-manual.html => focus-visible-003.html} (86%)
 create mode 100644 testing/web-platform/tests/element-timing/buffered-flag.html
 rename testing/web-platform/tests/{2dcontext => html/canvas/element/manual}/drawing-paths-to-the-canvas/canvas_focus_drawFocusIfNeeded_AAPI_001-manual.html (100%)
 rename testing/web-platform/tests/{2dcontext => html/canvas/element/manual}/drawing-paths-to-the-canvas/drawFocusIfNeeded_001.html (100%)
 rename testing/web-platform/tests/{2dcontext => html/canvas/element/manual}/drawing-paths-to-the-canvas/drawFocusIfNeeded_002.html (100%)
 rename testing/web-platform/tests/{2dcontext => html/canvas/element/manual}/drawing-paths-to-the-canvas/drawFocusIfNeeded_003.html (100%)
 rename testing/web-platform/tests/{2dcontext => html/canvas/element/manual}/drawing-paths-to-the-canvas/drawFocusIfNeeded_004.html (100%)
 rename testing/web-platform/tests/{2dcontext => html/canvas/element/manual}/drawing-paths-to-the-canvas/drawFocusIfNeeded_005.html (100%)
 create mode 100644 testing/web-platform/tests/longtask-timing/buffered-flag.window.js
 create mode 100644 testing/web-platform/tests/longtask-timing/containerTypes.html
 create mode 100644 testing/web-platform/tests/longtask-timing/long-microtask.window.js
 create mode 100644 testing/web-platform/tests/mathml/presentation-markup/direction/direction-006-ref.html
 create mode 100644 testing/web-platform/tests/mathml/presentation-markup/direction/direction-006.html
 create mode 100644 testing/web-platform/tests/mathml/presentation-markup/direction/direction-007-ref.html
 create mode 100644 testing/web-platform/tests/mathml/presentation-markup/direction/direction-007.html
 create mode 100644 testing/web-platform/tests/mathml/presentation-markup/direction/direction-008-ref.html
 create mode 100644 testing/web-platform/tests/mathml/presentation-markup/direction/direction-008.html
 create mode 100644 testing/web-platform/tests/mathml/presentation-markup/direction/direction-009-ref.html
 create mode 100644 testing/web-platform/tests/mathml/presentation-markup/direction/direction-009.html
 create mode 100644 testing/web-platform/tests/mathml/presentation-markup/direction/direction-010-ref.html
 create mode 100644 testing/web-platform/tests/mathml/presentation-markup/direction/direction-010.html
 create mode 100644 testing/web-platform/tests/mathml/relations/css-styling/attribute-mapping-001.html
 create mode 100644 testing/web-platform/tests/mathml/relations/css-styling/attribute-mapping-002.html
 delete mode 100644 testing/web-platform/tests/mathml/relations/css-styling/lengths-2-ref.html
 delete mode 100644 testing/web-platform/tests/mathml/relations/css-styling/lengths-3.html
 create mode 100644 testing/web-platform/tests/mathml/relations/css-styling/mathsize-attribute-css-keywords-ref.html
 create mode 100644 testing/web-platform/tests/mathml/relations/css-styling/mathsize-attribute-css-keywords.html
 create mode 100644 testing/web-platform/tests/mathml/relations/css-styling/mathsize-attribute-legacy-values-ref.html
 create mode 100644 testing/web-platform/tests/mathml/relations/css-styling/mathsize-attribute-legacy-values.html
 create mode 100644 testing/web-platform/tests/mathml/relations/css-styling/padding-border-margin/border-001.html
 create mode 100644 testing/web-platform/tests/mathml/relations/css-styling/padding-border-margin/border-002.html
 create mode 100644 testing/web-platform/tests/mathml/relations/css-styling/padding-border-margin/helper.js
 create mode 100644 testing/web-platform/tests/mathml/relations/css-styling/padding-border-margin/margin-001.html
 create mode 100644 testing/web-platform/tests/mathml/relations/css-styling/padding-border-margin/margin-002.html
 create mode 100644 testing/web-platform/tests/mathml/relations/css-styling/padding-border-margin/padding-001.html
 create mode 100644 testing/web-platform/tests/mathml/relations/css-styling/padding-border-margin/padding-002.html
 create mode 100644 testing/web-platform/tests/mathml/relations/css-styling/padding-border-margin/padding-003.html
 create mode 100644 testing/web-platform/tests/mathml/relations/css-styling/writing-mode/writing-mode-001.html
 create mode 100644 testing/web-platform/tests/mathml/support/layout-comparison.js
 create mode 100644 testing/web-platform/tests/mathml/support/mathml-fragments.js
 create mode 100644 testing/web-platform/tests/navigation-timing/buffered-flag.window.js
 create mode 100644 testing/web-platform/tests/navigation-timing/test_document_onload.html
 create mode 100644 testing/web-platform/tests/paint-timing/buffered-flag.window.js
 create mode 100644 testing/web-platform/tests/paint-timing/fcp-only/fcp-ensure-update-the-rendering-step.html
 create mode 100644 testing/web-platform/tests/paint-timing/fcp-only/fcp-text-input.html
 create mode 100644 testing/web-platform/tests/paint-timing/fcp-only/fcp-typographic-pseudo.html
 create mode 100644 testing/web-platform/tests/paint-timing/fcp-only/fcp-with-rtl.html
 create mode 100644 testing/web-platform/tests/performance-timeline/buffered-flag-after-timeout.any.js
 create mode 100644 testing/web-platform/tests/performance-timeline/buffered-flag-observer.any.js
 create mode 100644 testing/web-platform/tests/performance-timeline/multiple-buffered-flag-observers.any.js
 create mode 100644 testing/web-platform/tests/performance-timeline/observer-buffered-false.any.js
 create mode 100644 testing/web-platform/tests/performance-timeline/po-disconnect-removes-observed-types.any.js
 create mode 100644 testing/web-platform/tests/performance-timeline/po-observe-repeated-type.any.js
 create mode 100644 testing/web-platform/tests/resource-timing/buffered-flag.any.js
 create mode 100644 testing/web-platform/tests/user-timing/buffered-flag.any.js

diff --git a/testing/firefox-ui/tests/functional/keyboard_shortcuts/test_browser_window.py b/testing/firefox-ui/tests/functional/keyboard_shortcuts/test_browser_window.py
index d3f73f7468..dccd7ba7ea 100644
--- a/testing/firefox-ui/tests/functional/keyboard_shortcuts/test_browser_window.py
+++ b/testing/firefox-ui/tests/functional/keyboard_shortcuts/test_browser_window.py
@@ -47,7 +47,6 @@ class TestBrowserWindowShortcuts(PuppeteerMixin, MarionetteTestCase):
 
         # TODO: Check that the right input box is focused
         # Located below searchbar as class="textbox-input"
-        # Anon locator has not been released yet (bug 1080764)
         def has_input_selected(mn):
             selection_name = mn.execute_script("""
                 return window.document.activeElement.localName;
diff --git a/testing/firefox-ui/tests/functional/manifest.ini b/testing/firefox-ui/tests/functional/manifest.ini
index 791291e12d..32292c94fc 100644
--- a/testing/firefox-ui/tests/functional/manifest.ini
+++ b/testing/firefox-ui/tests/functional/manifest.ini
@@ -1,5 +1,4 @@
 [include:keyboard_shortcuts/manifest.ini]
-[include:private_browsing/manifest.ini]
 [include:safebrowsing/manifest.ini]
 [include:security/manifest.ini]
 [include:sessionstore/manifest.ini]
diff --git a/testing/firefox-ui/tests/functional/private_browsing/manifest.ini b/testing/firefox-ui/tests/functional/private_browsing/manifest.ini
deleted file mode 100644
index 34ef273653..0000000000
--- a/testing/firefox-ui/tests/functional/private_browsing/manifest.ini
+++ /dev/null
@@ -1,4 +0,0 @@
-[DEFAULT]
-tags = local
-
-[test_about_private_browsing.py]
diff --git a/testing/firefox-ui/tests/functional/private_browsing/test_about_private_browsing.py b/testing/firefox-ui/tests/functional/private_browsing/test_about_private_browsing.py
deleted file mode 100644
index 81d5e3df8c..0000000000
--- a/testing/firefox-ui/tests/functional/private_browsing/test_about_private_browsing.py
+++ /dev/null
@@ -1,73 +0,0 @@
-# This Source Code Form is subject to the terms of the Mozilla Public
-# License, v. 2.0. If a copy of the MPL was not distributed with this
-# file, You can obtain one at http://mozilla.org/MPL/2.0/.
-
-from __future__ import absolute_import
-from firefox_puppeteer import PuppeteerMixin
-from firefox_puppeteer.ui.browser.window import BrowserWindow
-from marionette_driver import By, Wait
-from marionette_harness import MarionetteTestCase
-
-
-class TestAboutPrivateBrowsingWithSearch(PuppeteerMixin, MarionetteTestCase):
-
-    def setUp(self):
-        super(TestAboutPrivateBrowsingWithSearch, self).setUp()
-
-        # Use a fake local support URL
-        support_url = 'about:blank?'
-        self.marionette.set_pref('app.support.baseURL', support_url)
-        self.pb_url = support_url + 'private-browsing-myths'
-
-    def tearDown(self):
-        try:
-            self.puppeteer.windows.close_all([self.browser])
-            self.browser.switch_to()
-
-            self.marionette.clear_pref('app.support.baseURL')
-        finally:
-            super(TestAboutPrivateBrowsingWithSearch, self).tearDown()
-
-    def testCheckAboutPrivateBrowsingWithSearch(self):
-        self.assertFalse(self.browser.is_private)
-
-        with self.marionette.using_context('content'):
-            self.marionette.navigate('about:privatebrowsing')
-
-            # Disabled awaiting support for Fluent strings in firefox-ui tests (bug 1534310)
-            # status_node = self.marionette.find_element(By.CSS_SELECTOR, 'p.showNormal')
-            # self.assertEqual(status_node.text,
-            #                 self.browser.localize_entity('aboutPrivateBrowsing.notPrivate'),
-            #                 'Status text indicates we are not in private browsing mode')
-
-        def window_opener(win):
-            with win.marionette.using_context('content'):
-                button = self.marionette.find_element(By.ID, 'startPrivateBrowsing')
-                button.click()
-
-        pb_window = self.browser.open_window(callback=window_opener,
-                                             expected_window_class=BrowserWindow)
-
-        try:
-            self.assertTrue(pb_window.is_private)
-
-            # Test the search hand-off
-            with self.marionette.using_context('content'):
-                search = self.marionette.find_element(By.ID, 'search-handoff-button')
-                search.click()
-
-            self.assertTrue(pb_window.navbar.locationbar.focused, 'url bar is focused')
-
-            pb_window.navbar.locationbar.urlbar.send_keys('foo')
-            self.assertEqual(pb_window.navbar.locationbar.value, '@google foo',
-                             'url bar prepends the @search shortcut')
-
-            # Test the private browsing myths link
-            with self.marionette.using_context('content'):
-                link = self.marionette.find_element(By.ID, 'private-browsing-myths')
-                link.click()
-                Wait(self.marionette, timeout=self.marionette.timeout.page_load).until(
-                    lambda _: self.marionette.get_url() == self.pb_url)
-
-        finally:
-            pb_window.close()
diff --git a/testing/firefox-ui/tests/puppeteer/test_toolbars.py b/testing/firefox-ui/tests/puppeteer/test_toolbars.py
index 689746db65..8b60af3814 100644
--- a/testing/firefox-ui/tests/puppeteer/test_toolbars.py
+++ b/testing/firefox-ui/tests/puppeteer/test_toolbars.py
@@ -85,27 +85,13 @@ class TestLocationBar(PuppeteerMixin, MarionetteTestCase):
         self.locationbar = self.browser.navbar.locationbar
 
     def test_elements(self):
-        self.assertEqual(self.locationbar.urlbar.get_property('localName'), 'textbox')
-        self.assertIn('urlbar-input', self.locationbar.urlbar_input.get_property('className'))
+        self.assertEqual(self.locationbar.urlbar_input.get_property('id'), 'urlbar-input')
 
-        self.assertEqual(self.locationbar.connection_icon.get_property('localName'), 'image')
-        self.assertEqual(self.locationbar.identity_box.get_property('localName'), 'box')
-        self.assertEqual(self.locationbar.identity_country_label.get_property('localName'),
-                         'label')
-        self.assertEqual(self.locationbar.identity_organization_label.get_property('localName'),
-                         'label')
-        self.assertEqual(self.locationbar.identity_icon.get_property('localName'), 'image')
-        self.assertEqual(self.locationbar.history_drop_marker.get_property('localName'),
-                         'dropmarker')
         self.assertEqual(self.locationbar.reload_button.get_property('localName'),
                          'toolbarbutton')
         self.assertEqual(self.locationbar.stop_button.get_property('localName'),
                          'toolbarbutton')
 
-        self.assertEqual(self.locationbar.contextmenu.get_property('localName'), 'menupopup')
-        self.assertEqual(self.locationbar.get_contextmenu_entry('paste').get_attribute('cmd'),
-                         'cmd_paste')
-
     def test_reload(self):
         event_types = ["shortcut", "shortcut2", "button"]
         for event in event_types:
@@ -131,83 +117,3 @@ class TestLocationBar(PuppeteerMixin, MarionetteTestCase):
 
         with self.marionette.using_context('content'):
             Wait(self.marionette).until(lambda mn: mn.get_url() == data_uri)
-
-
-class TestIdentityPopup(PuppeteerMixin, MarionetteTestCase):
-    def setUp(self):
-        super(TestIdentityPopup, self).setUp()
-
-        self.locationbar = self.browser.navbar.locationbar
-        self.identity_popup = self.locationbar.identity_popup
-
-        self.url = 'https://extended-validation.badssl.com'
-
-        with self.marionette.using_context('content'):
-            self.marionette.navigate(self.url)
-
-    def tearDown(self):
-        try:
-            self.identity_popup.close(force=True)
-        finally:
-            super(TestIdentityPopup, self).tearDown()
-
-    def test_elements(self):
-        self.locationbar.open_identity_popup()
-
-        # Test main view elements
-        main = self.identity_popup.view.main
-        self.assertEqual(main.element.get_property('localName'), 'panelview')
-
-        self.assertEqual(main.expander.get_property('localName'), 'button')
-        self.assertEqual(main.host.get_property('localName'), 'label')
-        self.assertEqual(main.insecure_connection_label.get_property('localName'),
-                         'description')
-        self.assertEqual(main.internal_connection_label.get_property('localName'),
-                         'description')
-        self.assertEqual(main.secure_connection_label.get_property('localName'),
-                         'description')
-
-        self.assertEqual(main.permissions.get_property('localName'), 'vbox')
-
-        # Test security view elements
-        security = self.identity_popup.view.security
-        self.assertEqual(security.element.get_property('localName'), 'panelview')
-
-        self.assertEqual(security.host.get_property('localName'), 'label')
-        self.assertEqual(security.insecure_connection_label.get_property('localName'),
-                         'description')
-        self.assertEqual(security.secure_connection_label.get_property('localName'),
-                         'description')
-
-        self.assertEqual(security.owner.get_property('localName'), 'description')
-        self.assertEqual(security.owner_location.get_property('localName'), 'description')
-        self.assertEqual(security.verifier.get_property('localName'), 'description')
-
-        self.assertEqual(security.disable_mixed_content_blocking_button.get_property('localName'),
-                         'button')
-        self.assertEqual(security.enable_mixed_content_blocking_button.get_property('localName'),
-                         'button')
-
-        self.assertEqual(security.more_info_button.get_property('localName'), 'button')
-
-    def test_open_close(self):
-        with self.marionette.using_context('content'):
-            self.marionette.navigate(self.url)
-
-        self.assertFalse(self.identity_popup.is_open)
-
-        self.locationbar.open_identity_popup()
-
-        self.identity_popup.close()
-        self.assertFalse(self.identity_popup.is_open)
-
-    def test_force_close(self):
-        with self.marionette.using_context('content'):
-            self.marionette.navigate(self.url)
-
-        self.assertFalse(self.identity_popup.is_open)
-
-        self.locationbar.open_identity_popup()
-
-        self.identity_popup.close(force=True)
-        self.assertFalse(self.identity_popup.is_open)
diff --git a/testing/firefox-ui/tests/puppeteer/test_windows.py b/testing/firefox-ui/tests/puppeteer/test_windows.py
index 849b7aa421..35327d2396 100644
--- a/testing/firefox-ui/tests/puppeteer/test_windows.py
+++ b/testing/firefox-ui/tests/puppeteer/test_windows.py
@@ -68,7 +68,7 @@ class TestWindows(PuppeteerMixin, MarionetteTestCase):
         def open_by_js(_):
             with self.marionette.using_context('chrome'):
                 self.marionette.execute_script("""
-                  window.open('chrome://browser/content/safeMode.xul', '_blank',
+                  window.open('chrome://browser/content/safeMode.xhtml', '_blank',
                               'chrome,centerscreen,resizable=no');
                 """)
 
diff --git a/testing/marionette/capture.js b/testing/marionette/capture.js
index 526ef39586..25f6a9dd63 100644
--- a/testing/marionette/capture.js
+++ b/testing/marionette/capture.js
@@ -41,20 +41,15 @@ capture.Format = {
  *
  * @param {Node} node
  *     The node to take a screenshot of.
- * @param {Array.<Node>=} highlights
- *     Optional array of nodes, around which a border will be marked to
- *     highlight them in the screenshot.
  *
  * @return {HTMLCanvasElement}
  *     The canvas element where the element has been painted on.
  */
-capture.element = function(node, highlights = []) {
+capture.element = function(node) {
   let win = node.ownerGlobal;
   let rect = node.getBoundingClientRect();
 
-  return capture.canvas(win, rect.left, rect.top, rect.width, rect.height, {
-    highlights,
-  });
+  return capture.canvas(win, rect.left, rect.top, rect.width, rect.height);
 };
 
 /**
@@ -64,21 +59,17 @@ capture.element = function(node, highlights = []) {
  * @param {DOMWindow} win
  *     The DOM window providing the document element to capture,
  *     and the offsets for the viewport.
- * @param {Array.<Node>=} highlights
- *     Optional array of nodes, around which a border will be marked to
- *     highlight them in the screenshot.
  *
  * @return {HTMLCanvasElement}
  *     The canvas element where the viewport has been painted on.
  */
-capture.viewport = function(win, highlights = []) {
+capture.viewport = function(win) {
   return capture.canvas(
     win,
     win.pageXOffset,
     win.pageYOffset,
     win.innerWidth,
-    win.innerHeight,
-    { highlights }
+    win.innerHeight
   );
 };
 
@@ -96,9 +87,6 @@ capture.viewport = function(win, highlights = []) {
  *     The width dimension of the rectangle to paint.
  * @param {number} height
  *     The height dimension of the rectangle to paint.
- * @param {Array.<Node>=} highlights
- *     Optional array of nodes, around which a border will be marked to
- *     highlight them in the screenshot.
  * @param {HTMLCanvasElement=} canvas
  *     Optional canvas to reuse for the screenshot.
  * @param {number=} flags
@@ -115,7 +103,7 @@ capture.canvas = function(
   top,
   width,
   height,
-  { highlights = [], canvas = null, flags = null } = {}
+  { canvas = null, flags = null } = {}
 ) {
   const scale = win.devicePixelRatio;
 
@@ -149,49 +137,20 @@ capture.canvas = function(
   let ctx = canvas.getContext(CONTEXT_2D);
   if (flags === null) {
     flags = ctx.DRAWWINDOW_DRAW_CARET;
-    // TODO(ato): https://bugzil.la/1377335
-    //
-    // Disabled in bug 1243415 for webplatform-test
-    // failures due to out of view elements.  Needs
-    // https://github.com/w3c/web-platform-tests/issues/4383 fixed.
-    /*
-    ctx.DRAWWINDOW_DRAW_VIEW;
-    */
-    // Bug 1009762 - Crash in [@ mozilla::gl::ReadPixelsIntoDataSurface]
-    /*
-    ctx.DRAWWINDOW_USE_WIDGET_LAYERS;
-    */
+
+    // Enabling those flags for drawWindow by default causes
+    // drawing failures. Wait until drawSnapshot is used and supports
+    // these flags (bug 1571341)
+    // ctx.DRAWWINDOW_DRAW_VIEW;
+    // ctx.DRAWWINDOW_USE_WIDGET_LAYERS;
   }
 
   ctx.scale(scale, scale);
   ctx.drawWindow(win, left, top, width, height, BG_COLOUR, flags);
-  if (highlights.length) {
-    ctx = capture.highlight_(ctx, highlights, top, left);
-  }
 
   return canvas;
 };
 
-capture.highlight_ = function(context, highlights, top = 0, left = 0) {
-  if (typeof highlights == "undefined") {
-    throw new InvalidArgumentError("Missing highlights");
-  }
-
-  context.lineWidth = "2";
-  context.strokeStyle = "red";
-  context.save();
-
-  for (let el of highlights) {
-    let rect = el.getBoundingClientRect();
-    let oy = -top;
-    let ox = -left;
-
-    context.strokeRect(rect.left + ox, rect.top + oy, rect.width, rect.height);
-  }
-
-  return context;
-};
-
 /**
  * Encode the contents of an HTMLCanvasElement to a Base64 encoded string.
  *
diff --git a/testing/marionette/chrome/test.xul b/testing/marionette/chrome/test.xhtml
similarity index 68%
rename from testing/marionette/chrome/test.xul
rename to testing/marionette/chrome/test.xhtml
index a81b93f1ad..e8165bc574 100644
--- a/testing/marionette/chrome/test.xul
+++ b/testing/marionette/chrome/test.xhtml
@@ -14,14 +14,14 @@
 
       <vbox id="things">
         <checkbox id="testBox"  label="box" />
-        <textbox id="textInput"  size="6" value="test" label="input" />
-        <textbox id="textInput2"  size="6" value="test" label="input" />
-        <textbox id="textInput3" class="asdf" size="6" value="test" label="input" />
+        <input xmlns="http://www.w3.org/1999/xhtml" id="textInput"  size="6" value="test" label="input" />
+        <input xmlns="http://www.w3.org/1999/xhtml" id="textInput2"  size="6" value="test" label="input" />
+        <input xmlns="http://www.w3.org/1999/xhtml" id="textInput3" class="asdf" size="6" value="test" label="input" />
       </vbox>
 
-      <iframe id="iframe" name="iframename" src="chrome://marionette/content/test2.xul"/>
-      <iframe id="iframe" name="iframename" src="chrome://marionette/content/test_nested_iframe.xul"/>
+      <iframe id="iframe" name="iframename" src="chrome://marionette/content/test2.xhtml"/>
+      <iframe id="iframe" name="iframename" src="chrome://marionette/content/test_nested_iframe.xhtml"/>
       <hbox id="testXulBox"/>
-      <browser id='aBrowser' src="chrome://marionette/content/test2.xul"/>
+      <browser id='aBrowser' src="chrome://marionette/content/test2.xhtml"/>
     </dialog>
 </window>
diff --git a/testing/marionette/chrome/test2.xhtml b/testing/marionette/chrome/test2.xhtml
new file mode 100644
index 0000000000..a02173c9c3
--- /dev/null
+++ b/testing/marionette/chrome/test2.xhtml
@@ -0,0 +1,20 @@
+<?xml version="1.0"?>
+<!-- This Source Code Form is subject to the terms of the Mozilla Public
+   - License, v. 2.0. If a copy of the MPL was not distributed with this
+   - file, You can obtain one at http://mozilla.org/MPL/2.0/. -->
+
+<!DOCTYPE window [
+]>
+
+<window xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">
+<dialog id="dia">
+
+  <vbox id="things">
+    <checkbox id="testBox"  label="box" />
+    <input xmlns="http://www.w3.org/1999/xhtml" id="textInput"  size="6" value="test" label="input" />
+    <input xmlns="http://www.w3.org/1999/xhtml" id="textInput2"  size="6" value="test" label="input" />
+    <input xmlns="http://www.w3.org/1999/xhtml" id="textInput3" class="asdf" size="6" value="test" label="input" />
+  </vbox>
+     
+</dialog>
+</window>
diff --git a/testing/marionette/chrome/test2.xul b/testing/marionette/chrome/test2.xul
deleted file mode 100644
index d450e03058..0000000000
--- a/testing/marionette/chrome/test2.xul
+++ /dev/null
@@ -1,19 +0,0 @@
-<?xml version="1.0"?>
-<!-- This Source Code Form is subject to the terms of the Mozilla Public
-   - License, v. 2.0. If a copy of the MPL was not distributed with this
-   - file, You can obtain one at http://mozilla.org/MPL/2.0/. -->
-
-<!DOCTYPE window [
-]>
-
-<dialog id="dia"
-            xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">
-
-  <vbox id="things">
-    <checkbox id="testBox"  label="box" />
-    <textbox id="textInput"  size="6" value="test" label="input" />
-    <textbox id="textInput2"  size="6" value="test" label="input" />
-    <textbox id="textInput3" class="asdf" size="6" value="test" label="input" />
-  </vbox>
-     
-</dialog>
diff --git a/testing/marionette/chrome/test_anonymous_content.xul b/testing/marionette/chrome/test_anonymous_content.xul
deleted file mode 100644
index 49f9eff292..0000000000
--- a/testing/marionette/chrome/test_anonymous_content.xul
+++ /dev/null
@@ -1,37 +0,0 @@
-<?xml version="1.0"?>
-<!-- This Source Code Form is subject to the terms of the Mozilla Public
-   - License, v. 2.0. If a copy of the MPL was not distributed with this
-   - file, You can obtain one at http://mozilla.org/MPL/2.0/. -->
-
-<!DOCTYPE dialog [
-]>
-
-<dialog id="testDialogAnonymousNode"
-          buttons="accept, cancel"
-          xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">
-
-  <bindings id="testBindings" xmlns="http://www.mozilla.org/xbl"
-            xmlns:xul="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">
-    <binding id="framebox">
-      <content orient="vertical" mousethrough="never">
-        <xul:browser anonid="content" id="browser" flex="1"
-                     context="contentAreaContextMenu"
-                     src="test.xul"
-                     type="content"/>
-      </content>
-    </binding>
-
-    <binding id="iframebox">
-      <content>
-        <xul:box>
-          <xul:iframe anonid="iframe" src="chrome://marionette/content/test.xul"></xul:iframe>
-        </xul:box>
-      </content>
-    </binding>
-  </bindings>
-
-  <hbox id="testAnonymousContentBox"/>
-  <hbox id="container" style="-moz-binding: url('#testBindings');"/>
-  <hbox id="container2" style="-moz-binding: url('#iframebox');"/>
-
-</dialog>
diff --git a/testing/marionette/chrome/test_dialog.xul b/testing/marionette/chrome/test_dialog.xhtml
similarity index 84%
rename from testing/marionette/chrome/test_dialog.xul
rename to testing/marionette/chrome/test_dialog.xhtml
index 0d4816b97e..5782a00d5e 100644
--- a/testing/marionette/chrome/test_dialog.xul
+++ b/testing/marionette/chrome/test_dialog.xhtml
@@ -11,9 +11,9 @@
 <?xml-stylesheet href="chrome://global/skin/" type="text/css"?>
 
 
+<window xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"
+        title="&testDialog.title;">
 <dialog id="testDialog"
-        xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul"
-        title="&testDialog.title;"
         buttons="accept,cancel">
 
   <vbox flex="1" style="min-width: 300px; min-height: 500px;">
@@ -29,8 +29,9 @@
     <checkbox id="check-box" label="Test Mode 2" />
     <hbox align="center">
       <label id="text-box-label" control="text-box">Name:</label>
-      <textbox id="text-box" flex="1" />
+      <input xmlns="http://www.w3.org/1999/xhtml" id="text-box" style="-moz-box-flex: 1;" />
     </hbox>
   </vbox>
 
 </dialog>
+</window>
diff --git a/testing/marionette/chrome/test_nested_iframe.xul b/testing/marionette/chrome/test_nested_iframe.xhtml
similarity index 81%
rename from testing/marionette/chrome/test_nested_iframe.xul
rename to testing/marionette/chrome/test_nested_iframe.xhtml
index 0bec83cbe6..1d0edcc65b 100644
--- a/testing/marionette/chrome/test_nested_iframe.xul
+++ b/testing/marionette/chrome/test_nested_iframe.xhtml
@@ -6,4 +6,4 @@
 <!DOCTYPE window [
 ]>
 
-  <iframe id="iframe" name="iframename" src="test2.xul"/>
+  <iframe id="iframe" name="iframename" src="test2.xhtml"/>
diff --git a/testing/marionette/client/docs/advanced/findelement.rst b/testing/marionette/client/docs/advanced/findelement.rst
index 778f8921a4..6f61fa5e25 100644
--- a/testing/marionette/client/docs/advanced/findelement.rst
+++ b/testing/marionette/client/docs/advanced/findelement.rst
@@ -85,42 +85,3 @@ Doing the following will work::
 But this will raise a `NoSuchElementException`::
 
     client.find_element(By.ID, 'container').find_element(By.ID, 'footer')
-
-
-Finding Anonymous Nodes
------------------------
-
-When working in chrome scope, for example manipulating the Firefox user
-interface, you may run into something called an anonymous node.
-
-Firefox uses a markup language called XUL_ for its interface. XUL is similar
-to HTML in that it has a DOM and tags that render controls on the display. One
-ability of XUL is to create re-useable widgets that are made up out of several
-smaller XUL elements. These widgets can be bound to the DOM using something
-called the `XML binding language (XBL)`_.
-
-The end result is that the DOM sees the widget as a single entity. It doesn't
-know anything about how that widget is made up. All of the smaller XUL elements
-that make up the widget are called `anonymous content`_. It is not possible to
-query such elements using traditional DOM methods like `getElementById`.
-
-Marionette provides two special strategies used for finding anonymous content.
-Unlike normal elements, anonymous nodes can only be seen by their parent. So
-it's necessary to first find the parent element and then search for the
-anonymous children from there.
-
-* `anon` - Finds all anonymous children of the element, there is no search term
-  so `None` must be passed in::
-
-    anon_children = client.find_element('id', 'parent').find_elements('anon', None)
-
-* `anon attribute` - Find an anonymous child based on an attribute. An
-  unofficial convention is for anonymous nodes to have an
-  `anonid` attribute::
-
-    anon_child = client.find_element('id', 'parent').find_element('anon attribute', {'anonid': 'container'})
-
-
-.. _XUL: https://developer.mozilla.org/en-US/docs/Mozilla/Tech/XUL
-.. _XML binding language (XBL): https://developer.mozilla.org/en-US/docs/XBL
-.. _anonymous content: https://developer.mozilla.org/en-US/docs/XBL/XBL_1.0_Reference/Anonymous_Content
diff --git a/testing/marionette/client/marionette_driver/by.py b/testing/marionette/client/marionette_driver/by.py
index 6427a8213c..9b0b611ac0 100644
--- a/testing/marionette/client/marionette_driver/by.py
+++ b/testing/marionette/client/marionette_driver/by.py
@@ -25,5 +25,3 @@ class By(object):
     TAG_NAME = "tag name"
     CLASS_NAME = "class name"
     CSS_SELECTOR = "css selector"
-    ANON_ATTRIBUTE = "anon attribute"
-    ANON = "anon"
diff --git a/testing/marionette/client/marionette_driver/marionette.py b/testing/marionette/client/marionette_driver/marionette.py
index 8343ceb08e..30ad38a79b 100644
--- a/testing/marionette/client/marionette_driver/marionette.py
+++ b/testing/marionette/client/marionette_driver/marionette.py
@@ -1677,9 +1677,9 @@ class Marionette(object):
 
         :param method: The method to use to locate the element; one of:
             "id", "name", "class name", "tag name", "css selector",
-            "link text", "partial link text", "xpath", "anon" and "anon
-            attribute". Note that the "name", "link text" and "partial
-            link test" methods are not supported in the chrome DOM.
+            "link text", "partial link text" and "xpath".
+            Note that the "name", "link text" and "partial link test"
+            methods are not supported in the chrome DOM.
         :param target: The target of the search.  For example, if method =
             "tag", target might equal "div".  If method = "id", target would
             be an element id.
@@ -1707,9 +1707,9 @@ class Marionette(object):
 
         :param method: The method to use to locate the elements; one
             of: "id", "name", "class name", "tag name", "css selector",
-            "link text", "partial link text", "xpath", "anon" and "anon
-            attribute". Note that the "name", "link text" and "partial link
-            test" methods are not supported in the chrome DOM.
+            "link text", "partial link text" and "xpath".
+            Note that the "name", "link text" and "partial link test"
+            methods are not supported in the chrome DOM.
         :param target: The target of the search.  For example, if method =
             "tag", target might equal "div".  If method = "id", target would be
             an element id.
@@ -1794,8 +1794,7 @@ class Marionette(object):
         """
         return self._send_message("WebDriver:GetCookies")
 
-    def save_screenshot(self, fh, element=None, highlights=None,
-                        full=True, scroll=True):
+    def save_screenshot(self, fh, element=None, full=True, scroll=True):
         """Takes a screenhot of a web element or the current frame and
         saves it in the filehandle.
 
@@ -1804,11 +1803,10 @@ class Marionette(object):
 
         The rest of the parameters are defined like in screenshot()
         """
-        data = self.screenshot(element, highlights, "binary", full, scroll)
+        data = self.screenshot(element, "binary", full, scroll)
         fh.write(data)
 
-    def screenshot(self, element=None, highlights=None, format="base64",
-                   full=True, scroll=True):
+    def screenshot(self, element=None, format="base64", full=True, scroll=True):
         """Takes a screenshot of a web element or the current frame.
 
         The screen capture is returned as a lossless PNG image encoded
@@ -1820,10 +1818,6 @@ class Marionette(object):
         :param element: The element to take a screenshot of.  If None, will
             take a screenshot of the current frame.
 
-        :param highlights: A list of
-            :class:`~marionette_driver.marionette.HTMLElement` objects to draw
-            a red box around in the returned screenshot.
-
         :param format: if "base64" (the default), returns the screenshot
             as a base64-string. If "binary", the data is decoded and
             returned as raw binary. If "hash", the data is hashed using
@@ -1840,12 +1834,8 @@ class Marionette(object):
 
         if element:
             element = element.id
-        lights = None
-        if highlights:
-            lights = [highlight.id for highlight in highlights]
 
         body = {"id": element,
-                "highlights": lights,
                 "full": full,
                 "hash": False,
                 "scroll": scroll}
diff --git a/testing/marionette/components/marionette.js b/testing/marionette/components/marionette.js
index f1511ef2a1..96513d538c 100644
--- a/testing/marionette/components/marionette.js
+++ b/testing/marionette/components/marionette.js
@@ -430,11 +430,12 @@ class MarionetteParentProcess {
     win.addEventListener(
       "load",
       () => {
-        if (win.document.getElementById("safeModeDialog")) {
+        let dialog = win.document.getElementById("safeModeDialog");
+        if (dialog) {
           // accept the dialog to start in safe-mode
           log.trace("Safe mode detected, supressing dialog");
           win.setTimeout(() => {
-            win.document.documentElement.getButton("accept").click();
+            dialog.getButton("accept").click();
           });
         }
       },
diff --git a/testing/marionette/doc/internals/element.rst b/testing/marionette/doc/internals/element.rst
index 2cad694947..5fabfc2c34 100644
--- a/testing/marionette/doc/internals/element.rst
+++ b/testing/marionette/doc/internals/element.rst
@@ -26,10 +26,6 @@ element.findByPartialLinkText
 -----------------------------
 .. js:autofunction:: element.findByPartialLinkText
 
-element.findAnonymousNodes
-----------------------------
-.. js:autofunction:: element.findAnonymousNodes
-
 element.findClosest
 -------------------
 .. js:autofunction:: element.findClosest
diff --git a/testing/marionette/driver.js b/testing/marionette/driver.js
index f1c06c28f6..62b0eeae51 100644
--- a/testing/marionette/driver.js
+++ b/testing/marionette/driver.js
@@ -98,8 +98,6 @@ const SUPPORTED_STRATEGIES = new Set([
   element.Strategy.ID,
   element.Strategy.TagName,
   element.Strategy.XPath,
-  element.Strategy.Anon,
-  element.Strategy.AnonAttribute,
 ]);
 
 // Timeout used to abort fullscreen, maximize, and minimize
@@ -1800,37 +1798,6 @@ GeckoDriver.prototype.switchToFrame = async function(cmd) {
         return;
       }
 
-      // Check if the frame is XBL anonymous
-      let parent = curWindow.document.getBindingParent(wantedFrame);
-      // Shadow nodes also show up in getAnonymousNodes, we should
-      // ignore them.
-      if (
-        parent &&
-        !(parent.shadowRoot && parent.shadowRoot.contains(wantedFrame))
-      ) {
-        const doc = curWindow.document;
-        let anonNodes = [...(doc.getAnonymousNodes(parent) || [])];
-        if (anonNodes.length > 0) {
-          let el = wantedFrame;
-          while (el) {
-            if (anonNodes.indexOf(el) > -1) {
-              curWindow = wantedFrame.contentWindow;
-              this.curFrame = curWindow;
-              if (focus) {
-                this.curFrame.focus();
-              }
-              checkTimer.initWithCallback(
-                checkLoad.bind(this),
-                100,
-                Ci.nsITimer.TYPE_ONE_SHOT
-              );
-              return;
-            }
-            el = el.parentNode;
-          }
-        }
-      }
-
       // else, assume iframe
       let frames = curWindow.document.getElementsByTagName("iframe");
       let numFrames = frames.length;
@@ -2656,7 +2623,7 @@ GeckoDriver.prototype.clearElement = async function(cmd) {
     case Context.Chrome:
       // the selenium atom doesn't work here
       let el = this.curBrowser.seenEls.get(webEl);
-      if (el.nodeName == "textbox") {
+      if (el.nodeName == "input" && el.type == "text") {
         el.value = "";
       } else if (el.nodeName == "checkbox") {
         el.checked = false;
@@ -2997,16 +2964,13 @@ GeckoDriver.prototype.deleteSession = function() {
  * @param {string=} id
  *     Optional web element reference to take a screenshot of.
  *     If undefined, a screenshot will be taken of the document element.
- * @param {Array.<string>=} highlights
- *     List of web elements to highlight.
- * @param {boolean} full
- *     True to take a screenshot of the entire document element. Is not
+ * @param {boolean=} full
+ *     True to take a screenshot of the entire document element. Is only
  *     considered if <var>id</var> is not defined. Defaults to true.
  * @param {boolean=} hash
- *     True if the user requests a hash of the image data.
+ *     True if the user requests a hash of the image data. Defaults to false.
  * @param {boolean=} scroll
- *     Scroll to element if |id| is provided.  If undefined, it will
- *     scroll to the element.
+ *     Scroll to element if |id| is provided. Defaults to true.
  *
  * @return {string}
  *     If <var>hash</var> is false, PNG image encoded as Base64 encoded
@@ -3016,23 +2980,21 @@ GeckoDriver.prototype.deleteSession = function() {
 GeckoDriver.prototype.takeScreenshot = function(cmd) {
   let win = assert.open(this.getCurrentWindow());
 
-  let { id, highlights, full, hash } = cmd.parameters;
-  highlights = highlights || [];
+  let { id, full, hash, scroll } = cmd.parameters;
   let format = hash ? capture.Format.Hash : capture.Format.Base64;
 
+  full = typeof full == "undefined" ? true : full;
+  scroll = typeof scroll == "undefined" ? true : scroll;
+
+  // Only consider full screenshot if no element has been specified
+  full = id ? false : full;
+
   switch (this.context) {
     case Context.Chrome:
-      let highlightEls = highlights
-        .map(ref => WebElement.fromUUID(ref, Context.Chrome))
-        .map(webEl => this.curBrowser.seenEls.get(webEl));
-
-      // viewport
       let canvas;
-      if (!id && !full) {
-        canvas = capture.viewport(win, highlightEls);
 
-        // element or full document element
-      } else {
+      // element or full document element
+      if (id || full) {
         let node;
         if (id) {
           let webEl = WebElement.fromUUID(id, Context.Chrome);
@@ -3041,7 +3003,11 @@ GeckoDriver.prototype.takeScreenshot = function(cmd) {
           node = win.document.documentElement;
         }
 
-        canvas = capture.element(node, highlightEls);
+        canvas = capture.element(node);
+
+        // viewport
+      } else {
+        canvas = capture.viewport(win);
       }
 
       switch (format) {
@@ -3054,7 +3020,11 @@ GeckoDriver.prototype.takeScreenshot = function(cmd) {
       break;
 
     case Context.Content:
-      return this.listener.takeScreenshot(format, cmd.parameters);
+      return this.listener.takeScreenshot(format, {
+        id,
+        full,
+        scroll,
+      });
   }
 
   throw new TypeError(`Unknown context: ${this.context}`);
diff --git a/testing/marionette/element.js b/testing/marionette/element.js
index 00e64991d1..9f560c53f9 100644
--- a/testing/marionette/element.js
+++ b/testing/marionette/element.js
@@ -82,8 +82,6 @@ element.Strategy = {
   PartialLinkText: "partial link text",
   TagName: "tag name",
   XPath: "xpath",
-  Anon: "anon",
-  AnonAttribute: "anon attribute",
 };
 
 /**
@@ -329,17 +327,7 @@ element.find = function(container, strategy, selector, opts = {}) {
       // the following code ought to be moved into findElement
       // and findElements when bug 1254486 is addressed
       if (!opts.all && (!foundEls || foundEls.length == 0)) {
-        let msg;
-        switch (strategy) {
-          case element.Strategy.AnonAttribute:
-            msg =
-              "Unable to locate anonymous element: " + JSON.stringify(selector);
-            break;
-
-          default:
-            msg = "Unable to locate element: " + selector;
-        }
-
+        let msg = `Unable to locate element: ${selector}`;
         reject(new NoSuchElementError(msg));
       }
 
@@ -361,19 +349,7 @@ function find_(
   let rootNode = container.shadowRoot || container.frame.document;
 
   if (!startNode) {
-    switch (strategy) {
-      // For anonymous nodes the start node needs to be of type
-      // DOMElement, which will refer to :root in case of a DOMDocument.
-      case element.Strategy.Anon:
-      case element.Strategy.AnonAttribute:
-        if (rootNode.nodeType == rootNode.DOCUMENT_NODE) {
-          startNode = rootNode.documentElement;
-        }
-        break;
-
-      default:
-        startNode = rootNode;
-    }
+    startNode = rootNode;
   }
 
   let res;
@@ -484,24 +460,6 @@ element.findByPartialLinkText = function(startNode, linkText) {
   );
 };
 
-/**
- * Find anonymous nodes of <var>node</var>.
- *
- * @param {XULDocument} document
- *     Root node of the document.
- * @param {XULElement} node
- *     Where in the DOM hierarchy to begin searching.
- *
- * @return {Iterable.<XULElement>}
- *     Iterator over anonymous elements.
- */
-element.findAnonymousNodes = function*(document, node) {
-  let anons = document.getAnonymousNodes(node) || [];
-  for (let node of anons) {
-    yield node;
-  }
-};
-
 /**
  * Filters all hyperlinks that are descendant of <var>startNode</var>
  * by <var>predicate</var>.
@@ -592,17 +550,6 @@ function findElement(strategy, selector, document, startNode = undefined) {
       } catch (e) {
         throw new InvalidSelectorError(`${e.message}: "${selector}"`);
       }
-
-    case element.Strategy.Anon:
-      return element.findAnonymousNodes(document, startNode).next().value;
-
-    case element.Strategy.AnonAttribute:
-      let attr = Object.keys(selector)[0];
-      return document.getAnonymousElementByAttribute(
-        startNode,
-        attr,
-        selector[attr]
-      );
   }
 
   throw new InvalidSelectorError(`No such strategy: ${strategy}`);
@@ -664,21 +611,6 @@ function findElements(strategy, selector, document, startNode = undefined) {
     case element.Strategy.Selector:
       return startNode.querySelectorAll(selector);
 
-    case element.Strategy.Anon:
-      return [...element.findAnonymousNodes(document, startNode)];
-
-    case element.Strategy.AnonAttribute:
-      let attr = Object.keys(selector)[0];
-      let el = document.getAnonymousElementByAttribute(
-        startNode,
-        attr,
-        selector[attr]
-      );
-      if (el) {
-        return [el];
-      }
-      return [];
-
     default:
       throw new InvalidSelectorError(`No such strategy: ${strategy}`);
   }
diff --git a/testing/marionette/harness/marionette_harness/__init__.py b/testing/marionette/harness/marionette_harness/__init__.py
index 4be3f4fa3d..4dafaa28e3 100644
--- a/testing/marionette/harness/marionette_harness/__init__.py
+++ b/testing/marionette/harness/marionette_harness/__init__.py
@@ -17,7 +17,6 @@ from .marionette_test import (
     skip_if_chrome,
     skip_if_desktop,
     skip_if_e10s,
-    skip_if_mobile,
     SkipTest,
     skip_unless_protocol,
 )
diff --git a/testing/marionette/harness/marionette_harness/marionette_test/__init__.py b/testing/marionette/harness/marionette_harness/marionette_test/__init__.py
index d163c5c881..f1d60b2740 100644
--- a/testing/marionette/harness/marionette_harness/marionette_test/__init__.py
+++ b/testing/marionette/harness/marionette_harness/marionette_test/__init__.py
@@ -19,7 +19,6 @@ from .decorators import (
     skip_if_chrome,
     skip_if_desktop,
     skip_if_e10s,
-    skip_if_mobile,
     skip_unless_browser_pref,
     skip_unless_protocol,
     with_parameters,
diff --git a/testing/marionette/harness/marionette_harness/marionette_test/decorators.py b/testing/marionette/harness/marionette_harness/marionette_test/decorators.py
index 9ecaa2e21e..9de2947760 100644
--- a/testing/marionette/harness/marionette_harness/marionette_test/decorators.py
+++ b/testing/marionette/harness/marionette_harness/marionette_test/decorators.py
@@ -139,21 +139,6 @@ def skip_if_e10s(reason):
     return decorator
 
 
-def skip_if_mobile(reason):
-    """Decorator which skips a test if run on mobile."""
-    def decorator(test_item):
-        if not isinstance(test_item, types.FunctionType):
-            raise Exception('Decorator only supported for functions')
-
-        @functools.wraps(test_item)
-        def skip_wrapper(self, *args, **kwargs):
-            if self.marionette.session_capabilities.get('browserName') == 'fennec':
-                raise SkipTest(reason)
-            return test_item(self, *args, **kwargs)
-        return skip_wrapper
-    return decorator
-
-
 def skip_unless_browser_pref(reason, pref, predicate=bool):
     """Decorator which skips a test based on the value of a browser preference.
 
diff --git a/testing/marionette/harness/marionette_harness/tests/unit/test_anonymous_content.py b/testing/marionette/harness/marionette_harness/tests/unit/test_anonymous_content.py
deleted file mode 100644
index 59984fee42..0000000000
--- a/testing/marionette/harness/marionette_harness/tests/unit/test_anonymous_content.py
+++ /dev/null
@@ -1,87 +0,0 @@
-# This Source Code Form is subject to the terms of the Mozilla Public
-# License, v. 2.0. If a copy of the MPL was not distributed with this
-# file, You can obtain one at http://mozilla.org/MPL/2.0/.
-
-from __future__ import absolute_import
-
-from marionette_driver.by import By
-from marionette_driver.errors import NoSuchElementException
-from marionette_driver.marionette import HTMLElement
-
-from marionette_harness import MarionetteTestCase, WindowManagerMixin
-
-
-class TestAnonymousNodes(WindowManagerMixin, MarionetteTestCase):
-
-    def setUp(self):
-        super(TestAnonymousNodes, self).setUp()
-        self.marionette.set_context("chrome")
-
-        url = "chrome://marionette/content/test_anonymous_content.xul"
-        new_window = self.open_chrome_window(url)
-        self.marionette.switch_to_window(new_window)
-
-    def tearDown(self):
-        self.close_all_windows()
-
-        super(TestAnonymousNodes, self).tearDown()
-
-    def test_switch_to_anonymous_frame(self):
-        self.marionette.find_element(By.ID, "testAnonymousContentBox")
-        anon_browser_el = self.marionette.find_element(By.ID, "browser")
-        self.assertTrue("test_anonymous_content.xul" in self.marionette.get_url())
-        self.marionette.switch_to_frame(anon_browser_el)
-        self.assertTrue("test.xul" in self.marionette.get_url())
-        self.marionette.find_element(By.ID, "testXulBox")
-        self.assertRaises(NoSuchElementException,
-                          self.marionette.find_element, By.ID, "testAnonymousContentBox")
-
-    def test_switch_to_anonymous_iframe(self):
-        self.marionette.find_element(By.ID, "testAnonymousContentBox")
-        el = self.marionette.find_element(By.ID, "container2")
-        anon_iframe_el = el.find_element(By.ANON_ATTRIBUTE, {"anonid": "iframe"})
-        self.marionette.switch_to_frame(anon_iframe_el)
-        self.assertTrue("test.xul" in self.marionette.get_url())
-        self.marionette.find_element(By.ID, "testXulBox")
-        self.assertRaises(NoSuchElementException, self.marionette.find_element, By.ID,
-                          "testAnonymousContentBox")
-
-    def test_find_anonymous_element_by_attribute(self):
-        accept_button = (By.ANON_ATTRIBUTE, {"dlgtype": "accept"},)
-        not_existent = (By.ANON_ATTRIBUTE, {"anonid": "notexistent"},)
-
-        # By using the window document element
-        start_node = self.marionette.find_element(By.CSS_SELECTOR, ":root")
-        button = start_node.find_element(*accept_button)
-        self.assertEquals(HTMLElement, type(button))
-        with self.assertRaises(NoSuchElementException):
-            start_node.find_element(*not_existent)
-
-        # By using the default start node
-        self.assertEquals(button, self.marionette.find_element(*accept_button))
-        with self.assertRaises(NoSuchElementException):
-            self.marionette.find_element(*not_existent)
-
-    def test_find_anonymous_elements_by_attribute(self):
-        dialog_buttons = (By.ANON_ATTRIBUTE, {"anonid": "buttons"},)
-        not_existent = (By.ANON_ATTRIBUTE, {"anonid": "notexistent"},)
-
-        # By using the window document element
-        start_node = self.marionette.find_element(By.CSS_SELECTOR, ":root")
-        buttons = start_node.find_elements(*dialog_buttons)
-        self.assertEquals(1, len(buttons))
-        self.assertEquals(HTMLElement, type(buttons[0]))
-        self.assertListEqual([], start_node.find_elements(*not_existent))
-
-        # By using the default start node
-        self.assertListEqual(buttons, self.marionette.find_elements(*dialog_buttons))
-        self.assertListEqual([], self.marionette.find_elements(*not_existent))
-
-    def test_find_anonymous_children(self):
-        self.assertEquals(HTMLElement, type(self.marionette.find_element(By.ANON, None)))
-        self.assertEquals(3, len(self.marionette.find_elements(By.ANON, None)))
-
-        frame = self.marionette.find_element(By.ID, "framebox")
-        with self.assertRaises(NoSuchElementException):
-            frame.find_element(By.ANON, None)
-        self.assertListEqual([], frame.find_elements(By.ANON, None))
diff --git a/testing/marionette/harness/marionette_harness/tests/unit/test_checkbox_chrome.py b/testing/marionette/harness/marionette_harness/tests/unit/test_checkbox_chrome.py
index 7740f6cebe..8e3e579a23 100644
--- a/testing/marionette/harness/marionette_harness/tests/unit/test_checkbox_chrome.py
+++ b/testing/marionette/harness/marionette_harness/tests/unit/test_checkbox_chrome.py
@@ -16,7 +16,7 @@ class TestSelectedChrome(WindowManagerMixin, MarionetteTestCase):
 
         self.marionette.set_context("chrome")
 
-        new_window = self.open_chrome_window("chrome://marionette/content/test.xul")
+        new_window = self.open_chrome_window("chrome://marionette/content/test.xhtml")
         self.marionette.switch_to_window(new_window)
 
     def tearDown(self):
diff --git a/testing/marionette/harness/marionette_harness/tests/unit/test_click.py b/testing/marionette/harness/marionette_harness/tests/unit/test_click.py
index 3c82af6820..1967d00b3b 100644
--- a/testing/marionette/harness/marionette_harness/tests/unit/test_click.py
+++ b/testing/marionette/harness/marionette_harness/tests/unit/test_click.py
@@ -12,7 +12,6 @@ from marionette_driver.marionette import Alert
 from marionette_harness import (
     MarionetteTestCase,
     run_if_e10s,
-    skip_if_mobile,
     WindowManagerMixin,
 )
 
@@ -453,7 +452,6 @@ class TestClickCloseContext(WindowManagerMixin, MarionetteTestCase):
         self.marionette.navigate(self.test_page)
         self.marionette.find_element(By.ID, "close-window").click()
 
-    @skip_if_mobile("Fennec doesn't support other chrome windows")
     def test_click_close_window(self):
         new_tab = self.open_window()
         self.marionette.switch_to_window(new_tab)
diff --git a/testing/marionette/harness/marionette_harness/tests/unit/test_click_chrome.py b/testing/marionette/harness/marionette_harness/tests/unit/test_click_chrome.py
index 1bdae76e22..91cde8e538 100644
--- a/testing/marionette/harness/marionette_harness/tests/unit/test_click_chrome.py
+++ b/testing/marionette/harness/marionette_harness/tests/unit/test_click_chrome.py
@@ -22,7 +22,7 @@ class TestClickChrome(WindowManagerMixin, MarionetteTestCase):
         super(TestClickChrome, self).tearDown()
 
     def test_click(self):
-        win = self.open_chrome_window("chrome://marionette/content/test.xul")
+        win = self.open_chrome_window("chrome://marionette/content/test.xhtml")
         self.marionette.switch_to_window(win)
 
         def checked():
diff --git a/testing/marionette/harness/marionette_harness/tests/unit/test_element_state_chrome.py b/testing/marionette/harness/marionette_harness/tests/unit/test_element_state_chrome.py
index d5f863710b..3f04976bbc 100644
--- a/testing/marionette/harness/marionette_harness/tests/unit/test_element_state_chrome.py
+++ b/testing/marionette/harness/marionette_harness/tests/unit/test_element_state_chrome.py
@@ -16,7 +16,7 @@ class TestElementState(WindowManagerMixin, MarionetteTestCase):
 
         self.marionette.set_context("chrome")
 
-        self.win = self.open_chrome_window("chrome://marionette/content/test.xul")
+        self.win = self.open_chrome_window("chrome://marionette/content/test.xhtml")
         self.marionette.switch_to_window(self.win)
 
     def tearDown(self):
diff --git a/testing/marionette/harness/marionette_harness/tests/unit/test_elementsize_chrome.py b/testing/marionette/harness/marionette_harness/tests/unit/test_elementsize_chrome.py
index 7c6878537b..b426bb6016 100644
--- a/testing/marionette/harness/marionette_harness/tests/unit/test_elementsize_chrome.py
+++ b/testing/marionette/harness/marionette_harness/tests/unit/test_elementsize_chrome.py
@@ -16,7 +16,7 @@ class TestElementSizeChrome(WindowManagerMixin, MarionetteTestCase):
 
         self.marionette.set_context("chrome")
 
-        new_window = self.open_chrome_window("chrome://marionette/content/test2.xul")
+        new_window = self.open_chrome_window("chrome://marionette/content/test2.xhtml")
         self.marionette.switch_to_window(new_window)
 
     def tearDown(self):
diff --git a/testing/marionette/harness/marionette_harness/tests/unit/test_execute_sandboxes.py b/testing/marionette/harness/marionette_harness/tests/unit/test_execute_sandboxes.py
index 7fbf0dcc09..6c7966338b 100644
--- a/testing/marionette/harness/marionette_harness/tests/unit/test_execute_sandboxes.py
+++ b/testing/marionette/harness/marionette_harness/tests/unit/test_execute_sandboxes.py
@@ -6,7 +6,7 @@ from __future__ import absolute_import
 
 from marionette_driver.errors import JavascriptException
 
-from marionette_harness import MarionetteTestCase, skip_if_mobile
+from marionette_harness import MarionetteTestCase
 
 
 class TestExecuteSandboxes(MarionetteTestCase):
@@ -41,7 +41,6 @@ class TestExecuteSandboxes(MarionetteTestCase):
             "return foo", sandbox="2", new_sandbox=False)
         self.assertEqual(foo, 2)
 
-    @skip_if_mobile("Intermittent on Android - bug 1526914")
     def test_execute_new_sandbox(self):
         # test that clearing a sandbox does not affect other sandboxes
         self.marionette.execute_script("foo = 1", sandbox="1")
diff --git a/testing/marionette/harness/marionette_harness/tests/unit/test_execute_script.py b/testing/marionette/harness/marionette_harness/tests/unit/test_execute_script.py
index 1127c46f8f..fe4b59b80e 100644
--- a/testing/marionette/harness/marionette_harness/tests/unit/test_execute_script.py
+++ b/testing/marionette/harness/marionette_harness/tests/unit/test_execute_script.py
@@ -7,7 +7,7 @@ from marionette_driver import By, errors
 from marionette_driver.marionette import Alert, HTMLElement
 from marionette_driver.wait import Wait
 
-from marionette_harness import MarionetteTestCase, skip_if_mobile, WindowManagerMixin
+from marionette_harness import MarionetteTestCase, WindowManagerMixin
 
 
 def inline(doc):
@@ -351,7 +351,6 @@ class TestExecuteContent(MarionetteTestCase):
     def test_comment_in_last_line(self):
         self.marionette.execute_script(" // comment ")
 
-    @skip_if_mobile("Modal dialogs not supported in Fennec")
     def test_return_value_on_alert(self):
         res = self.marionette._send_message("WebDriver:ExecuteScript", {"script": "alert()"})
         self.assertIn("value", res)
@@ -372,15 +371,15 @@ class TestExecuteChrome(WindowManagerMixin, TestExecuteContent):
         self.marionette.execute_script(
             "Components.classes['@mozilla.org/preferences-service;1']")
 
-    @skip_if_mobile("New windows not supported in Fennec")
     def test_unmarshal_element_collection(self):
         try:
-            win = self.open_chrome_window("chrome://marionette/content/test.xul")
+            win = self.open_chrome_window("chrome://marionette/content/test.xhtml")
             self.marionette.switch_to_window(win)
 
-            expected = self.marionette.find_elements(By.TAG_NAME, "textbox")
+            expected = self.marionette.find_elements(By.TAG_NAME, "input")
             actual = self.marionette.execute_script(
-                "return document.querySelectorAll('textbox')")
+                "return document.querySelectorAll('input')")
+            self.assertTrue(len(expected) > 0)
             self.assertEqual(expected, actual)
 
         finally:
diff --git a/testing/marionette/harness/marionette_harness/tests/unit/test_findelement_chrome.py b/testing/marionette/harness/marionette_harness/tests/unit/test_findelement_chrome.py
index 0c999747da..3063bf5bdf 100644
--- a/testing/marionette/harness/marionette_harness/tests/unit/test_findelement_chrome.py
+++ b/testing/marionette/harness/marionette_harness/tests/unit/test_findelement_chrome.py
@@ -18,7 +18,7 @@ class TestElementsChrome(WindowManagerMixin, MarionetteTestCase):
 
         self.marionette.set_context("chrome")
 
-        win = self.open_chrome_window("chrome://marionette/content/test.xul")
+        win = self.open_chrome_window("chrome://marionette/content/test.xhtml")
         self.marionette.switch_to_window(win)
 
     def tearDown(self):
@@ -41,14 +41,14 @@ class TestElementsChrome(WindowManagerMixin, MarionetteTestCase):
     def test_child_element(self):
         el = self.marionette.find_element(By.ID, "textInput")
         parent = self.marionette.find_element(By.ID, "things")
-        found_el = parent.find_element(By.TAG_NAME, "textbox")
+        found_el = parent.find_element(By.TAG_NAME, "input")
         self.assertEqual(HTMLElement, type(found_el))
         self.assertEqual(el, found_el)
 
     def test_child_elements(self):
         el = self.marionette.find_element(By.ID, "textInput3")
         parent = self.marionette.find_element(By.ID, "things")
-        found_els = parent.find_elements(By.TAG_NAME, "textbox")
+        found_els = parent.find_elements(By.TAG_NAME, "input")
         self.assertTrue(el.id in [found_el.id for found_el in found_els])
 
     def test_tag_name(self):
@@ -85,7 +85,7 @@ class TestElementsChrome(WindowManagerMixin, MarionetteTestCase):
         self.marionette.timeout.implicit = 4
         self.marionette.execute_script("""
             window.setTimeout(function () {
-              var b = window.document.createElement('button');
+              var b = window.document.createXULElement('button');
               b.id = 'myid';
               document.getElementById('things').appendChild(b);
             }, 1000); """)
diff --git a/testing/marionette/harness/marionette_harness/tests/unit/test_get_current_url_chrome.py b/testing/marionette/harness/marionette_harness/tests/unit/test_get_current_url_chrome.py
index d43d6815e2..3168eb033d 100644
--- a/testing/marionette/harness/marionette_harness/tests/unit/test_get_current_url_chrome.py
+++ b/testing/marionette/harness/marionette_harness/tests/unit/test_get_current_url_chrome.py
@@ -6,7 +6,7 @@ from __future__ import absolute_import
 
 from marionette_driver.errors import NoSuchWindowException
 
-from marionette_harness import MarionetteTestCase, WindowManagerMixin, skip_if_mobile
+from marionette_harness import MarionetteTestCase, WindowManagerMixin
 
 
 class TestGetCurrentUrlChrome(WindowManagerMixin, MarionetteTestCase):
@@ -29,9 +29,8 @@ class TestGetCurrentUrlChrome(WindowManagerMixin, MarionetteTestCase):
         chrome_url = self.marionette.execute_script("return window.location.href;")
         self.assertEqual(self.marionette.get_url(), chrome_url)
 
-    @skip_if_mobile("Fennec doesn't support other chrome windows")
     def test_no_browser_window(self):
-        win = self.open_chrome_window("chrome://marionette/content/test.xul")
+        win = self.open_chrome_window("chrome://marionette/content/test.xhtml")
         self.marionette.switch_to_window(win)
 
         chrome_url = self.marionette.execute_script("return window.location.href;")
diff --git a/testing/marionette/harness/marionette_harness/tests/unit/test_marionette.py b/testing/marionette/harness/marionette_harness/tests/unit/test_marionette.py
index 0b89c9cf91..1acdbbc4f5 100644
--- a/testing/marionette/harness/marionette_harness/tests/unit/test_marionette.py
+++ b/testing/marionette/harness/marionette_harness/tests/unit/test_marionette.py
@@ -9,7 +9,7 @@ import time
 
 from marionette_driver import errors
 from marionette_driver.marionette import Marionette
-from marionette_harness import MarionetteTestCase, run_if_manage_instance, skip_if_mobile
+from marionette_harness import MarionetteTestCase, run_if_manage_instance
 
 
 class TestMarionette(MarionetteTestCase):
@@ -25,7 +25,6 @@ class TestMarionette(MarionetteTestCase):
         self.assertIn(expected_test_name, self.marionette.test_name)
 
     @run_if_manage_instance("Only runnable if Marionette manages the instance")
-    @skip_if_mobile("Bug 1322993 - Missing temporary folder")
     def test_raise_for_port_non_existing_process(self):
         """Test that raise_for_port doesn't run into a timeout if instance is not running."""
         self.marionette.quit()
@@ -61,7 +60,6 @@ class TestMarionette(MarionetteTestCase):
         self.assertEqual(current_socket_timeout,
                          self.marionette.client._sock.gettimeout())
 
-    @skip_if_mobile("No application update service available on Android")
     def test_application_update_disabled(self):
         # Updates of the application should always be disabled by default
         with self.marionette.using_context("chrome"):
diff --git a/testing/marionette/harness/marionette_harness/tests/unit/test_mouse_action.py b/testing/marionette/harness/marionette_harness/tests/unit/test_mouse_action.py
index 1755f244c0..f03aca2ed6 100644
--- a/testing/marionette/harness/marionette_harness/tests/unit/test_mouse_action.py
+++ b/testing/marionette/harness/marionette_harness/tests/unit/test_mouse_action.py
@@ -9,7 +9,7 @@ import urllib
 from marionette_driver import By, errors, Wait
 from marionette_driver.keys import Keys
 
-from marionette_harness import MarionetteTestCase, skip_if_mobile
+from marionette_harness import MarionetteTestCase
 
 
 def inline(doc):
@@ -78,7 +78,6 @@ class TestPointerActions(BaseMouseAction):
         event_count = self.marionette.execute_script("return window.eventCount", sandbox=None)
         self.assertEqual(event_count, 2)
 
-    @skip_if_mobile("There is no context menu available on mobile")
     def test_context_click_action(self):
         test_html = self.marionette.absolute_url("clicks.html")
         self.marionette.navigate(test_html)
@@ -151,7 +150,6 @@ class TestNonSpecCompliantPointerOrigin(BaseMouseAction):
         self.assertAlmostEqual(click_position["x"], elem_center_point["x"], delta=1)
         self.assertAlmostEqual(click_position["y"], elem_center_point["y"], delta=1)
 
-    @skip_if_mobile("Bug 1534291 - Missing MoveTargetOutOfBoundsException")
     def test_click_element_larger_than_viewport_with_center_point_outside(self):
         self.marionette.navigate(inline("""
           <div id="div" style="width: 300vw; height: 300vh; background: green;"
diff --git a/testing/marionette/harness/marionette_harness/tests/unit/test_navigation.py b/testing/marionette/harness/marionette_harness/tests/unit/test_navigation.py
index 6bfb620c96..04c2bab585 100644
--- a/testing/marionette/harness/marionette_harness/tests/unit/test_navigation.py
+++ b/testing/marionette/harness/marionette_harness/tests/unit/test_navigation.py
@@ -15,7 +15,6 @@ from marionette_harness import (
     MarionetteTestCase,
     run_if_e10s,
     run_if_manage_instance,
-    skip_if_mobile,
     WindowManagerMixin,
 )
 
@@ -258,14 +257,12 @@ class TestNavigate(BaseNavigationTestCase):
         self.marionette.go_back()
         self.assertEqual(self.marionette.get_url(), self.test_page_push_state)
 
-    @skip_if_mobile("Test file is only located on host machine")
     def test_navigate_file_url(self):
         self.marionette.navigate(self.test_page_file_url)
         self.marionette.find_element(By.ID, "file-url")
         self.marionette.navigate(self.test_page_remote)
 
     @run_if_e10s("Requires e10s mode enabled")
-    @skip_if_mobile("Test file is only located on host machine")
     def test_navigate_file_url_remoteness_change(self):
         self.marionette.navigate("about:robots")
         self.assertFalse(self.is_remote_tab)
@@ -283,7 +280,6 @@ class TestNavigate(BaseNavigationTestCase):
         self.marionette.navigate("about:blank")
 
     @run_if_manage_instance("Only runnable if Marionette manages the instance")
-    @skip_if_mobile("Bug 1322993 - Missing temporary folder")
     def test_focus_after_navigation(self):
         self.marionette.restart()
 
@@ -299,13 +295,12 @@ class TestNavigate(BaseNavigationTestCase):
         self.marionette.switch_to_window(self.new_tab)
         self.marionette.navigate(self.test_page_remote)
 
-    @skip_if_mobile("Interacting with chrome elements not available for Fennec")
     def test_type_to_non_remote_tab(self):
         self.marionette.navigate(self.test_page_not_remote)
         self.assertFalse(self.is_remote_tab)
 
         with self.marionette.using_context("chrome"):
-            urlbar = self.marionette.find_element(By.ID, "urlbar")
+            urlbar = self.marionette.find_element(By.ID, "urlbar-input")
             urlbar.send_keys(self.mod_key + "a")
             urlbar.send_keys(self.mod_key + "x")
             urlbar.send_keys("about:support" + Keys.ENTER)
@@ -315,13 +310,12 @@ class TestNavigate(BaseNavigationTestCase):
             message="'about:support' hasn't been loaded")
         self.assertFalse(self.is_remote_tab)
 
-    @skip_if_mobile("Interacting with chrome elements not available for Fennec")
     @run_if_e10s("Requires e10s mode enabled")
     def test_type_to_remote_tab(self):
         self.assertTrue(self.is_remote_tab)
 
         with self.marionette.using_context("chrome"):
-            urlbar = self.marionette.find_element(By.ID, "urlbar")
+            urlbar = self.marionette.find_element(By.ID, "urlbar-input")
             urlbar.send_keys(self.mod_key + "a")
             urlbar.send_keys(self.mod_key + "x")
             urlbar.send_keys(self.test_page_remote + Keys.ENTER)
@@ -431,7 +425,6 @@ class TestBackForwardNavigation(BaseNavigationTestCase):
         ]
         self.run_bfcache_test(test_pages)
 
-    @skip_if_mobile("Test file is only located on host machine")
     def test_file_url(self):
         test_pages = [
             {"url": self.test_page_remote},
@@ -521,7 +514,6 @@ class TestBackForwardNavigation(BaseNavigationTestCase):
         ]
         self.run_bfcache_test(test_pages)
 
-    @skip_if_mobile("Bug 1333209 - Process killed because of connection loss")
     def test_non_remote_about_pages(self):
         test_pages = [
             {"url": "about:preferences", "is_remote": False},
@@ -620,7 +612,6 @@ class TestRefresh(BaseNavigationTestCase):
         self.marionette.refresh()
         self.marionette.find_element(By.NAME, "third")
 
-    @skip_if_mobile("Test file is only located on host machine")
     def test_file_url(self):
         self.marionette.navigate(self.test_page_file_url)
         self.assertEqual(self.test_page_file_url, self.marionette.get_url())
diff --git a/testing/marionette/harness/marionette_harness/tests/unit/test_pagesource_chrome.py b/testing/marionette/harness/marionette_harness/tests/unit/test_pagesource_chrome.py
index 70f493a291..7ac0fa57c9 100644
--- a/testing/marionette/harness/marionette_harness/tests/unit/test_pagesource_chrome.py
+++ b/testing/marionette/harness/marionette_harness/tests/unit/test_pagesource_chrome.py
@@ -13,7 +13,7 @@ class TestPageSourceChrome(WindowManagerMixin, MarionetteTestCase):
         super(TestPageSourceChrome, self).setUp()
         self.marionette.set_context("chrome")
 
-        new_window = self.open_chrome_window("chrome://marionette/content/test.xul")
+        new_window = self.open_chrome_window("chrome://marionette/content/test.xhtml")
         self.marionette.switch_to_window(new_window)
 
     def tearDown(self):
@@ -22,4 +22,4 @@ class TestPageSourceChrome(WindowManagerMixin, MarionetteTestCase):
 
     def testShouldReturnXULDetails(self):
         source = self.marionette.page_source
-        self.assertTrue('<textbox id="textInput"' in source)
+        self.assertTrue('<input xmlns="http://www.w3.org/1999/xhtml" id="textInput"' in source)
diff --git a/testing/marionette/harness/marionette_harness/tests/unit/test_prefs.py b/testing/marionette/harness/marionette_harness/tests/unit/test_prefs.py
index 2f12572d3e..1d1f20e9b2 100644
--- a/testing/marionette/harness/marionette_harness/tests/unit/test_prefs.py
+++ b/testing/marionette/harness/marionette_harness/tests/unit/test_prefs.py
@@ -10,8 +10,6 @@ from marionette_driver.errors import JavascriptException
 from marionette_harness import (
     MarionetteTestCase,
     run_if_manage_instance,
-    skip_if_desktop,
-    skip_if_mobile
 )
 
 
@@ -43,7 +41,6 @@ class TestPreferences(MarionetteTestCase):
                 self.assertEqual(self.marionette.get_pref(key), value,
                                  "Preference {} hasn't been set to {}".format(key, repr(value)))
 
-    @skip_if_mobile("Only runnable with Firefox")
     def test_desktop_instance_preferences(self):
         required_prefs = geckoinstance.DesktopInstance.desktop_prefs
 
@@ -54,17 +51,6 @@ class TestPreferences(MarionetteTestCase):
             self.assertEqual(self.marionette.get_pref(key), value,
                              "Preference {} hasn't been set to {}".format(key, value))
 
-    @skip_if_desktop("Only runnable with Fennec")
-    def test_fennec_instance_preferences(self):
-        required_prefs = geckoinstance.FennecInstance.required_prefs
-
-        for key, value in required_prefs.iteritems():
-            if key in ["browser.tabs.remote.autostart"]:
-                return
-
-            self.assertEqual(self.marionette.get_pref(key), value,
-                             "Preference {} hasn't been set to {}".format(key, value))
-
     def test_clear_pref(self):
         self.assertIsNone(self.marionette.get_pref(self.prefs["bool"]))
 
diff --git a/testing/marionette/harness/marionette_harness/tests/unit/test_screen_orientation.py b/testing/marionette/harness/marionette_harness/tests/unit/test_screen_orientation.py
index a61fa3be95..89cfd6ff4b 100644
--- a/testing/marionette/harness/marionette_harness/tests/unit/test_screen_orientation.py
+++ b/testing/marionette/harness/marionette_harness/tests/unit/test_screen_orientation.py
@@ -10,7 +10,6 @@ from marionette_harness import (
     MarionetteTestCase,
     parameterized,
     skip_if_desktop,
-    skip_if_mobile,
 )
 
 
@@ -22,12 +21,8 @@ class TestScreenOrientation(MarionetteTestCase):
 
     def setUp(self):
         MarionetteTestCase.setUp(self)
-        self.is_mobile = self.marionette.session_capabilities.get("rotatable", False)
 
     def tearDown(self):
-        if self.is_mobile:
-            self.marionette.set_orientation(default_orientation)
-            self.wait_for_orientation(default_orientation)
         MarionetteTestCase.tearDown(self)
 
     def wait_for_orientation(self, orientation, timeout=None):
@@ -75,7 +70,6 @@ class TestScreenOrientation(MarionetteTestCase):
                                      unknown_orientation.format("null")):
             self.marionette.set_orientation(None)
 
-    @skip_if_mobile("Specific test for Firefox")
     def test_unsupported_operation_on_desktop(self):
         with self.assertRaises(errors.UnsupportedOperationException):
             self.marionette.set_orientation("landscape-primary")
diff --git a/testing/marionette/harness/marionette_harness/tests/unit/test_screenshot.py b/testing/marionette/harness/marionette_harness/tests/unit/test_screenshot.py
index 9f5e2c05a7..e61d606791 100644
--- a/testing/marionette/harness/marionette_harness/tests/unit/test_screenshot.py
+++ b/testing/marionette/harness/marionette_harness/tests/unit/test_screenshot.py
@@ -8,15 +8,16 @@ import base64
 import hashlib
 import imghdr
 import struct
+import sys
 import tempfile
+import unittest
 import urllib
 
 from marionette_driver import By
-from marionette_driver.errors import NoSuchElementException, NoSuchWindowException
+from marionette_driver.errors import NoSuchWindowException
 from marionette_harness import (
     MarionetteTestCase,
     skip,
-    skip_if_mobile,
     WindowManagerMixin,
 )
 
@@ -135,7 +136,7 @@ class TestScreenCaptureChrome(WindowManagerMixin, ScreenCaptureTestCase):
             """))
 
     def open_dialog(self):
-        return self.open_chrome_window("chrome://marionette/content/test_dialog.xul")
+        return self.open_chrome_window("chrome://marionette/content/test_dialog.xhtml")
 
     def test_capture_different_context(self):
         """Check that screenshots in content and chrome are different."""
@@ -144,7 +145,6 @@ class TestScreenCaptureChrome(WindowManagerMixin, ScreenCaptureTestCase):
         screenshot_chrome = self.marionette.screenshot()
         self.assertNotEqual(screenshot_content, screenshot_chrome)
 
-    @skip_if_mobile("Fennec doesn't support other chrome windows")
     def test_capture_element(self):
         dialog = self.open_dialog()
         self.marionette.switch_to_window(dialog)
@@ -162,8 +162,6 @@ class TestScreenCaptureChrome(WindowManagerMixin, ScreenCaptureTestCase):
         self.marionette.close_chrome_window()
         self.marionette.switch_to_window(self.start_window)
 
-    # @skip_if_mobile("Fennec doesn't support other chrome windows")
-    @skip("Bug 1329424 - AssertionError: u'iVBORw0KGgoA... (images unexpectedly equal)")
     def test_capture_flags(self):
         dialog = self.open_dialog()
         self.marionette.switch_to_window(dialog)
@@ -192,7 +190,6 @@ class TestScreenCaptureChrome(WindowManagerMixin, ScreenCaptureTestCase):
         self.assertEqual(self.scale(self.get_element_dimensions(self.document_element)),
                          self.get_image_dimensions(screenshot_full))
 
-    @skip_if_mobile("Fennec doesn't support other chrome windows")
     def test_capture_window_already_closed(self):
         dialog = self.open_dialog()
         self.marionette.switch_to_window(dialog)
@@ -201,7 +198,6 @@ class TestScreenCaptureChrome(WindowManagerMixin, ScreenCaptureTestCase):
         self.assertRaises(NoSuchWindowException, self.marionette.screenshot)
         self.marionette.switch_to_window(self.start_window)
 
-    @skip_if_mobile("Fennec doesn't support other chrome windows")
     def test_formats(self):
         dialog = self.open_dialog()
         self.marionette.switch_to_window(dialog)
@@ -215,46 +211,6 @@ class TestScreenCaptureChrome(WindowManagerMixin, ScreenCaptureTestCase):
         with self.assertRaises(ValueError):
             self.marionette.screenshot(format="cheese")
 
-    @skip_if_mobile("Fennec doesn't support other chrome windows")
-    def test_highlight_elements(self):
-        dialog = self.open_dialog()
-        self.marionette.switch_to_window(dialog)
-
-        # Highlighting the element itself shouldn't make the image larger
-        element = self.marionette.find_element(By.ID, "test-list")
-        screenshot_element = self.marionette.screenshot(element=element)
-        screenshot_highlight = self.marionette.screenshot(element=element,
-                                                          highlights=[element])
-        self.assertEqual(self.scale(self.get_element_dimensions(element)),
-                         self.get_image_dimensions(screenshot_element))
-        self.assertNotEqual(screenshot_element, screenshot_highlight)
-
-        # Highlighting a sub element
-        button = self.marionette.find_element(By.ID, "choose-button")
-        screenshot_highlight_button = self.marionette.screenshot(element=element,
-                                                                 highlights=[button])
-        self.assertNotEqual(screenshot_element, screenshot_highlight_button)
-        self.assertNotEqual(screenshot_highlight, screenshot_highlight_button)
-
-        self.marionette.close_chrome_window()
-        self.marionette.switch_to_window(self.start_window)
-
-    def test_highlight_element_not_seen(self):
-        """Check that for not found elements an exception is raised."""
-        with self.marionette.using_context('content'):
-            self.marionette.navigate(box)
-            content_element = self.marionette.find_element(By.ID, "green")
-
-        self.assertRaisesRegexp(NoSuchElementException, "Web element reference not seen before",
-                                self.marionette.screenshot, highlights=[content_element])
-
-        chrome_document_element = self.document_element
-        with self.marionette.using_context('content'):
-            self.assertRaisesRegexp(NoSuchElementException,
-                                    "Web element reference not seen before",
-                                    self.marionette.screenshot,
-                                    highlights=[chrome_document_element])
-
 
 class TestScreenCaptureContent(WindowManagerMixin, ScreenCaptureTestCase):
 
@@ -280,7 +236,6 @@ class TestScreenCaptureContent(WindowManagerMixin, ScreenCaptureTestCase):
         self.assertRaises(NoSuchWindowException, self.marionette.screenshot)
         self.marionette.switch_to_window(self.start_tab)
 
-    @skip_if_mobile("Bug 1487124 - Android need its own maximum allowed dimensions")
     def test_capture_vertical_bounds(self):
         self.marionette.navigate(inline("<body style='margin-top: 32768px'>foo"))
         screenshot = self.marionette.screenshot()
@@ -304,7 +259,7 @@ class TestScreenCaptureContent(WindowManagerMixin, ScreenCaptureTestCase):
                          self.get_image_dimensions(screenshot))
         self.assertGreater(self.page_y_offset, 0)
 
-    @skip("Bug 1330560 - AssertionError: u'iVBORw0KGgoA... (images unexpectedly equal)")
+    @unittest.skipIf(sys.platform.startswith("win"), "Bug 1330560")
     def test_capture_flags(self):
         self.marionette.navigate(input)
 
@@ -361,25 +316,6 @@ class TestScreenCaptureContent(WindowManagerMixin, ScreenCaptureTestCase):
         with self.assertRaises(ValueError):
             self.marionette.screenshot(format="cheese")
 
-    def test_highlight_elements(self):
-        self.marionette.navigate(box)
-        element = self.marionette.find_element(By.TAG_NAME, "div")
-
-        # Highlighting the element itself shouldn't make the image larger
-        screenshot_element = self.marionette.screenshot(element=element)
-        screenshot_highlight = self.marionette.screenshot(element=element,
-                                                          highlights=[element])
-        self.assertEqual(self.scale(self.get_element_dimensions(element)),
-                         self.get_image_dimensions(screenshot_highlight))
-        self.assertNotEqual(screenshot_element, screenshot_highlight)
-
-        # Highlighting a sub element
-        paragraph = self.marionette.find_element(By.ID, "green")
-        screenshot_highlight_paragraph = self.marionette.screenshot(element=element,
-                                                                    highlights=[paragraph])
-        self.assertNotEqual(screenshot_element, screenshot_highlight_paragraph)
-        self.assertNotEqual(screenshot_highlight, screenshot_highlight_paragraph)
-
     def test_save_screenshot(self):
         expected = self.marionette.screenshot(format="binary")
         with tempfile.TemporaryFile('w+b') as fh:
diff --git a/testing/marionette/harness/marionette_harness/tests/unit/test_switch_frame_chrome.py b/testing/marionette/harness/marionette_harness/tests/unit/test_switch_frame_chrome.py
index 3d71590e76..d79f235c9b 100644
--- a/testing/marionette/harness/marionette_harness/tests/unit/test_switch_frame_chrome.py
+++ b/testing/marionette/harness/marionette_harness/tests/unit/test_switch_frame_chrome.py
@@ -15,7 +15,7 @@ class TestSwitchFrameChrome(WindowManagerMixin, MarionetteTestCase):
         super(TestSwitchFrameChrome, self).setUp()
         self.marionette.set_context("chrome")
 
-        new_window = self.open_chrome_window("chrome://marionette/content/test.xul")
+        new_window = self.open_chrome_window("chrome://marionette/content/test.xhtml")
         self.marionette.switch_to_window(new_window)
         self.assertNotEqual(self.start_window, self.marionette.current_chrome_window_handle)
 
@@ -24,26 +24,26 @@ class TestSwitchFrameChrome(WindowManagerMixin, MarionetteTestCase):
         super(TestSwitchFrameChrome, self).tearDown()
 
     def test_switch_simple(self):
-        self.assertIn("test.xul", self.marionette.get_url(), "Initial navigation has failed")
+        self.assertIn("test.xhtml", self.marionette.get_url(), "Initial navigation has failed")
         self.marionette.switch_to_frame(0)
-        self.assertIn("test2.xul", self.marionette.get_url(),"Switching by index failed")
+        self.assertIn("test2.xhtml", self.marionette.get_url(),"Switching by index failed")
         self.marionette.switch_to_frame()
         self.assertEqual(None, self.marionette.get_active_frame(), "Switiching by null failed")
-        self.assertIn("test.xul", self.marionette.get_url(), "Switching by null failed")
+        self.assertIn("test.xhtml", self.marionette.get_url(), "Switching by null failed")
         self.marionette.switch_to_frame("iframe")
-        self.assertIn("test2.xul", self.marionette.get_url(), "Switching by name failed")
+        self.assertIn("test2.xhtml", self.marionette.get_url(), "Switching by name failed")
         self.marionette.switch_to_frame()
-        self.assertIn("test.xul", self.marionette.get_url(), "Switching by null failed")
+        self.assertIn("test.xhtml", self.marionette.get_url(), "Switching by null failed")
         self.marionette.switch_to_frame("iframename")
-        self.assertIn("test2.xul", self.marionette.get_url(), "Switching by name failed")
+        self.assertIn("test2.xhtml", self.marionette.get_url(), "Switching by name failed")
         iframe_element = self.marionette.get_active_frame()
         self.marionette.switch_to_frame()
-        self.assertIn("test.xul", self.marionette.get_url(), "Switching by null failed")
+        self.assertIn("test.xhtml", self.marionette.get_url(), "Switching by null failed")
         self.marionette.switch_to_frame(iframe_element)
-        self.assertIn("test2.xul", self.marionette.get_url(), "Switching by element failed")
+        self.assertIn("test2.xhtml", self.marionette.get_url(), "Switching by element failed")
 
     def test_stack_trace(self):
-        self.assertIn("test.xul", self.marionette.get_url(), "Initial navigation has failed")
+        self.assertIn("test.xhtml", self.marionette.get_url(), "Initial navigation has failed")
         self.marionette.switch_to_frame(0)
         self.assertRaises(JavascriptException, self.marionette.execute_async_script, "foo();")
         try:
diff --git a/testing/marionette/harness/marionette_harness/tests/unit/test_switch_window_content.py b/testing/marionette/harness/marionette_harness/tests/unit/test_switch_window_content.py
index 2ffb71edb3..8549e2390a 100644
--- a/testing/marionette/harness/marionette_harness/tests/unit/test_switch_window_content.py
+++ b/testing/marionette/harness/marionette_harness/tests/unit/test_switch_window_content.py
@@ -9,7 +9,6 @@ from marionette_driver.keys import Keys
 
 from marionette_harness import (
     MarionetteTestCase,
-    skip_if_mobile,
     WindowManagerMixin,
 )
 
@@ -89,7 +88,6 @@ class TestSwitchToWindowContent(WindowManagerMixin, MarionetteTestCase):
         self.assertEqual(self.marionette.current_window_handle, self.start_tab)
         self.assertEqual(self.get_selected_tab_index(), self.selected_tab_index)
 
-    @skip_if_mobile("Fennec doesn't support other chrome windows")
     def test_switch_tabs_in_different_windows_with_focus_change(self):
         new_tab1 = self.open_tab(focus=True)
         self.assertEqual(self.marionette.current_window_handle, self.start_tab)
diff --git a/testing/marionette/harness/marionette_harness/tests/unit/test_timeouts.py b/testing/marionette/harness/marionette_harness/tests/unit/test_timeouts.py
index f058634004..da5bfd0a55 100644
--- a/testing/marionette/harness/marionette_harness/tests/unit/test_timeouts.py
+++ b/testing/marionette/harness/marionette_harness/tests/unit/test_timeouts.py
@@ -12,7 +12,7 @@ from marionette_driver.errors import (
 )
 from marionette_driver.marionette import HTMLElement
 
-from marionette_harness import MarionetteTestCase, run_if_manage_instance, skip_if_mobile
+from marionette_harness import MarionetteTestCase, run_if_manage_instance
 
 
 class TestTimeouts(MarionetteTestCase):
@@ -65,7 +65,6 @@ class TestTimeouts(MarionetteTestCase):
         self.assertRaises(NoSuchElementException, self.marionette.find_element, By.ID, "newDiv")
 
     @run_if_manage_instance("Only runnable if Marionette manages the instance")
-    @skip_if_mobile("Bug 1322993 - Missing temporary folder")
     def test_reset_timeout(self):
         timeouts = [getattr(self.marionette.timeout, f) for f in (
             'implicit', 'page_load', 'script',)]
diff --git a/testing/marionette/harness/marionette_harness/tests/unit/test_title_chrome.py b/testing/marionette/harness/marionette_harness/tests/unit/test_title_chrome.py
index 90fa5a89b2..cbd1f9dfbc 100644
--- a/testing/marionette/harness/marionette_harness/tests/unit/test_title_chrome.py
+++ b/testing/marionette/harness/marionette_harness/tests/unit/test_title_chrome.py
@@ -20,7 +20,7 @@ class TestTitleChrome(WindowManagerMixin, MarionetteTestCase):
         super(TestTitleChrome, self).tearDown()
 
     def test_get_chrome_title(self):
-        win = self.open_chrome_window("chrome://marionette/content/test.xul")
+        win = self.open_chrome_window("chrome://marionette/content/test.xhtml")
         self.marionette.switch_to_window(win)
 
         title = self.marionette.execute_script(
diff --git a/testing/marionette/harness/marionette_harness/tests/unit/test_typing.py b/testing/marionette/harness/marionette_harness/tests/unit/test_typing.py
index f2bc800081..037befad26 100644
--- a/testing/marionette/harness/marionette_harness/tests/unit/test_typing.py
+++ b/testing/marionette/harness/marionette_harness/tests/unit/test_typing.py
@@ -10,7 +10,7 @@ from marionette_driver.by import By
 from marionette_driver.errors import ElementNotInteractableException
 from marionette_driver.keys import Keys
 
-from marionette_harness import MarionetteTestCase, skip, skip_if_mobile
+from marionette_harness import MarionetteTestCase, skip
 
 
 def inline(doc):
@@ -34,7 +34,6 @@ class TestTypingChrome(TypingTestCase):
         super(TestTypingChrome, self).setUp()
         self.marionette.set_context("chrome")
 
-    @skip_if_mobile("Interacting with chrome elements not available for Fennec")
     def test_cut_and_paste_shortcuts(self):
         with self.marionette.using_context("content"):
             test_html = self.marionette.absolute_url("keyboard.html")
@@ -50,12 +49,12 @@ class TestTypingChrome(TypingTestCase):
             key_reporter.send_keys(self.mod_key, "x")
             self.assertEqual("", key_reporter.get_property("value"))
 
-        url_bar = self.marionette.find_element(By.ID, "urlbar")
+        url_bar = self.marionette.find_element(By.ID, "urlbar-input")
 
         # Clear contents first
         url_bar.send_keys(self.mod_key, "a")
         url_bar.send_keys(Keys.BACK_SPACE)
-        self.assertEqual("", url_bar.get_attribute("value"))
+        self.assertEqual("", url_bar.get_property("value"))
 
         url_bar.send_keys(self.mod_key, "v")
         self.assertEqual("zyxwvutsr", url_bar.get_property("value"))
@@ -215,7 +214,6 @@ class TestTypingContent(TypingTestCase):
         #  filled, we're a letter short here
         self.assertEqual(result.text, "I like chees")
 
-    @skip_if_mobile("Bug 1333069 - Assertion: 'down: 40' not found in u''")
     def test_should_report_key_code_of_arrow_keys_up_down_events(self):
         test_html = self.marionette.absolute_url("keyboard.html")
         self.marionette.navigate(test_html)
diff --git a/testing/marionette/harness/marionette_harness/tests/unit/test_window_close_chrome.py b/testing/marionette/harness/marionette_harness/tests/unit/test_window_close_chrome.py
index 79d9d6ddef..f604ecd59d 100644
--- a/testing/marionette/harness/marionette_harness/tests/unit/test_window_close_chrome.py
+++ b/testing/marionette/harness/marionette_harness/tests/unit/test_window_close_chrome.py
@@ -31,7 +31,7 @@ class TestCloseWindow(WindowManagerMixin, MarionetteTestCase):
         self.assertNotIn(new_window, self.marionette.window_handles)
 
     def test_close_chrome_window_for_non_browser_window(self):
-        win = self.open_chrome_window("chrome://marionette/content/test.xul")
+        win = self.open_chrome_window("chrome://marionette/content/test.xhtml")
         self.marionette.switch_to_window(win)
 
         self.assertIn(win, self.marionette.chrome_window_handles)
diff --git a/testing/marionette/harness/marionette_harness/tests/unit/test_window_close_content.py b/testing/marionette/harness/marionette_harness/tests/unit/test_window_close_content.py
index bc0b791c90..8864b1329b 100644
--- a/testing/marionette/harness/marionette_harness/tests/unit/test_window_close_content.py
+++ b/testing/marionette/harness/marionette_harness/tests/unit/test_window_close_content.py
@@ -7,7 +7,7 @@ from __future__ import absolute_import
 import urllib
 
 from marionette_driver.by import By
-from marionette_harness import MarionetteTestCase, skip_if_mobile, WindowManagerMixin
+from marionette_harness import MarionetteTestCase, WindowManagerMixin
 
 
 def inline(doc):
@@ -22,7 +22,6 @@ class TestCloseWindow(WindowManagerMixin, MarionetteTestCase):
 
         super(TestCloseWindow, self).tearDown()
 
-    @skip_if_mobile("Interacting with chrome windows not available for Fennec")
     def test_close_chrome_window_for_browser_window(self):
         with self.marionette.using_context("chrome"):
             new_window = self.open_window()
@@ -34,9 +33,8 @@ class TestCloseWindow(WindowManagerMixin, MarionetteTestCase):
         self.assertListEqual(self.start_windows, chrome_window_handles)
         self.assertNotIn(new_window, self.marionette.window_handles)
 
-    @skip_if_mobile("Interacting with chrome windows not available for Fennec")
     def test_close_chrome_window_for_non_browser_window(self):
-        new_window = self.open_chrome_window("chrome://marionette/content/test.xul")
+        new_window = self.open_chrome_window("chrome://marionette/content/test.xhtml")
         self.marionette.switch_to_window(new_window)
 
         self.assertIn(new_window, self.marionette.chrome_window_handles)
@@ -46,7 +44,6 @@ class TestCloseWindow(WindowManagerMixin, MarionetteTestCase):
         self.assertListEqual(self.start_windows, chrome_window_handles)
         self.assertNotIn(new_window, self.marionette.window_handles)
 
-    @skip_if_mobile("Interacting with chrome windows not available for Fennec")
     def test_close_chrome_window_for_last_open_window(self):
         self.close_all_windows()
 
@@ -79,7 +76,6 @@ class TestCloseWindow(WindowManagerMixin, MarionetteTestCase):
         self.marionette.find_element(By.TAG_NAME, "input").send_keys("foo")
         self.marionette.close()
 
-    @skip_if_mobile("Interacting with chrome windows not available for Fennec")
     def test_close_window_for_browser_window_with_single_tab(self):
         new_tab = self.open_window()
         self.marionette.switch_to_window(new_tab)
@@ -98,7 +94,6 @@ class TestCloseWindow(WindowManagerMixin, MarionetteTestCase):
         self.assertListEqual([self.start_window], self.marionette.chrome_window_handles)
         self.assertIsNotNone(self.marionette.session)
 
-    @skip_if_mobile("discardBrowser is only available in Firefox")
     def test_close_browserless_tab(self):
         self.close_all_tabs()
 
diff --git a/testing/marionette/harness/marionette_harness/tests/unit/test_window_handles_chrome.py b/testing/marionette/harness/marionette_harness/tests/unit/test_window_handles_chrome.py
index b55cc45f93..9e05d11f41 100644
--- a/testing/marionette/harness/marionette_harness/tests/unit/test_window_handles_chrome.py
+++ b/testing/marionette/harness/marionette_harness/tests/unit/test_window_handles_chrome.py
@@ -16,7 +16,7 @@ class TestWindowHandles(WindowManagerMixin, MarionetteTestCase):
     def setUp(self):
         super(TestWindowHandles, self).setUp()
 
-        self.xul_dialog = "chrome://marionette/content/test_dialog.xul"
+        self.chrome_dialog = "chrome://marionette/content/test_dialog.xhtml"
 
         self.marionette.set_context("chrome")
 
@@ -46,7 +46,7 @@ class TestWindowHandles(WindowManagerMixin, MarionetteTestCase):
         self.assertIn(new_browser, self.marionette.chrome_window_handles)
         self.assertEqual(self.marionette.current_chrome_window_handle, self.start_window)
 
-        new_dialog = self.open_chrome_window(self.xul_dialog)
+        new_dialog = self.open_chrome_window(self.chrome_dialog)
         self.assert_window_handles()
         self.assertEqual(len(self.marionette.chrome_window_handles), len(self.start_windows) + 2)
         self.assertIn(new_dialog, self.marionette.chrome_window_handles)
@@ -62,7 +62,7 @@ class TestWindowHandles(WindowManagerMixin, MarionetteTestCase):
                              window_handles_in_chrome_scope)
 
     def test_chrome_window_handles_after_opening_new_chrome_window(self):
-        new_window = self.open_chrome_window(self.xul_dialog)
+        new_window = self.open_chrome_window(self.chrome_dialog)
         self.assert_window_handles()
         self.assertEqual(len(self.marionette.chrome_window_handles), len(self.start_windows) + 1)
         self.assertIn(new_window, self.marionette.chrome_window_handles)
@@ -72,7 +72,7 @@ class TestWindowHandles(WindowManagerMixin, MarionetteTestCase):
         self.marionette.switch_to_window(new_window)
         self.assert_window_handles()
         self.assertEqual(self.marionette.current_chrome_window_handle, new_window)
-        self.assertEqual(self.marionette.get_url(), self.xul_dialog)
+        self.assertEqual(self.marionette.get_url(), self.chrome_dialog)
 
         # Close the chrome window, and carry on in our original window.
         self.marionette.close_chrome_window()
@@ -158,7 +158,7 @@ class TestWindowHandles(WindowManagerMixin, MarionetteTestCase):
         self.assertEqual(self.marionette.current_window_handle, self.start_tab)
 
     def test_window_handles_after_opening_new_chrome_window(self):
-        new_window = self.open_chrome_window(self.xul_dialog)
+        new_window = self.open_chrome_window(self.chrome_dialog)
         self.assert_window_handles()
         self.assertEqual(len(self.marionette.window_handles), len(self.start_tabs))
         self.assertNotIn(new_window, self.marionette.window_handles)
@@ -166,7 +166,7 @@ class TestWindowHandles(WindowManagerMixin, MarionetteTestCase):
 
         self.marionette.switch_to_window(new_window)
         self.assert_window_handles()
-        self.assertEqual(self.marionette.get_url(), self.xul_dialog)
+        self.assertEqual(self.marionette.get_url(), self.chrome_dialog)
 
         # Check that the opened dialog is not accessible via window handles
         with self.assertRaises(errors.NoSuchWindowException):
diff --git a/testing/marionette/harness/marionette_harness/tests/unit/test_window_handles_content.py b/testing/marionette/harness/marionette_harness/tests/unit/test_window_handles_content.py
index bc95f9a30b..4b90b4a27e 100644
--- a/testing/marionette/harness/marionette_harness/tests/unit/test_window_handles_content.py
+++ b/testing/marionette/harness/marionette_harness/tests/unit/test_window_handles_content.py
@@ -9,7 +9,7 @@ import urllib
 
 from marionette_driver import errors
 
-from marionette_harness import MarionetteTestCase, skip_if_mobile, WindowManagerMixin
+from marionette_harness import MarionetteTestCase, WindowManagerMixin
 
 
 def inline(doc):
@@ -21,7 +21,7 @@ class TestWindowHandles(WindowManagerMixin, MarionetteTestCase):
     def setUp(self):
         super(TestWindowHandles, self).setUp()
 
-        self.xul_dialog = "chrome://marionette/content/test_dialog.xul"
+        self.chrome_dialog = "chrome://marionette/content/test_dialog.xhtml"
 
     def tearDown(self):
         self.close_all_tabs()
@@ -78,9 +78,8 @@ class TestWindowHandles(WindowManagerMixin, MarionetteTestCase):
         self.assert_window_handles()
         self.assertEqual(self.marionette.current_window_handle, self.start_tab)
 
-    @skip_if_mobile("Fennec doesn't support other chrome windows")
     def tst_window_handles_after_opening_new_non_browser_window(self):
-        new_window = self.open_chrome_window(self.xul_dialog)
+        new_window = self.open_chrome_window(self.chrome_dialog)
         self.assert_window_handles()
         self.assertEqual(len(self.marionette.window_handles), len(self.start_tabs))
         self.assertEqual(self.marionette.current_window_handle, self.start_tab)
diff --git a/testing/marionette/harness/marionette_harness/tests/unit/test_window_management.py b/testing/marionette/harness/marionette_harness/tests/unit/test_window_management.py
index 0a0062b028..d6f1ae4d51 100644
--- a/testing/marionette/harness/marionette_harness/tests/unit/test_window_management.py
+++ b/testing/marionette/harness/marionette_harness/tests/unit/test_window_management.py
@@ -7,7 +7,7 @@ from __future__ import absolute_import
 from marionette_driver import By
 from marionette_driver.errors import NoSuchWindowException
 
-from marionette_harness import MarionetteTestCase, WindowManagerMixin, skip_if_mobile
+from marionette_harness import MarionetteTestCase, WindowManagerMixin
 
 
 class TestNoSuchWindowContent(WindowManagerMixin, MarionetteTestCase):
@@ -19,7 +19,6 @@ class TestNoSuchWindowContent(WindowManagerMixin, MarionetteTestCase):
         self.close_all_tabs()
         super(TestNoSuchWindowContent, self).tearDown()
 
-    @skip_if_mobile("Fennec doesn't support other chrome windows")
     def test_closed_chrome_window(self):
         with self.marionette.using_context("chrome"):
             new_window = self.open_window()
@@ -39,9 +38,8 @@ class TestNoSuchWindowContent(WindowManagerMixin, MarionetteTestCase):
         with self.assertRaises(NoSuchWindowException):
             self.marionette.switch_to_window(new_window)
 
-    @skip_if_mobile("Fennec doesn't support other chrome windows")
     def test_closed_chrome_window_while_in_frame(self):
-        new_window = self.open_chrome_window("chrome://marionette/content/test.xul")
+        new_window = self.open_chrome_window("chrome://marionette/content/test.xhtml")
         self.marionette.switch_to_window(new_window)
         with self.marionette.using_context("chrome"):
             self.marionette.switch_to_frame("iframe")
diff --git a/testing/marionette/harness/marionette_harness/tests/unit/test_window_status_content.py b/testing/marionette/harness/marionette_harness/tests/unit/test_window_status_content.py
index c9aee1cbbc..c4d496e549 100644
--- a/testing/marionette/harness/marionette_harness/tests/unit/test_window_status_content.py
+++ b/testing/marionette/harness/marionette_harness/tests/unit/test_window_status_content.py
@@ -7,7 +7,7 @@ from __future__ import absolute_import
 from marionette_driver import By
 from marionette_driver.errors import NoSuchWindowException
 
-from marionette_harness import MarionetteTestCase, WindowManagerMixin, skip_if_mobile
+from marionette_harness import MarionetteTestCase, WindowManagerMixin
 
 
 class TestNoSuchWindowContent(WindowManagerMixin, MarionetteTestCase):
@@ -19,7 +19,6 @@ class TestNoSuchWindowContent(WindowManagerMixin, MarionetteTestCase):
         self.close_all_windows()
         super(TestNoSuchWindowContent, self).tearDown()
 
-    @skip_if_mobile("Fennec doesn't support other chrome windows")
     def test_closed_chrome_window(self):
         with self.marionette.using_context("chrome"):
             new_window = self.open_window()
@@ -39,9 +38,8 @@ class TestNoSuchWindowContent(WindowManagerMixin, MarionetteTestCase):
         with self.assertRaises(NoSuchWindowException):
             self.marionette.switch_to_window(new_window)
 
-    @skip_if_mobile("Fennec doesn't support other chrome windows")
     def test_closed_chrome_window_while_in_frame(self):
-        new_window = self.open_chrome_window("chrome://marionette/content/test.xul")
+        new_window = self.open_chrome_window("chrome://marionette/content/test.xhtml")
         self.marionette.switch_to_window(new_window)
 
         with self.marionette.using_context("chrome"):
diff --git a/testing/marionette/harness/marionette_harness/tests/unit/test_window_type_chrome.py b/testing/marionette/harness/marionette_harness/tests/unit/test_window_type_chrome.py
index ce0a6ec686..fcf29b74e0 100644
--- a/testing/marionette/harness/marionette_harness/tests/unit/test_window_type_chrome.py
+++ b/testing/marionette/harness/marionette_harness/tests/unit/test_window_type_chrome.py
@@ -20,7 +20,7 @@ class TestWindowTypeChrome(WindowManagerMixin, MarionetteTestCase):
         super(TestWindowTypeChrome, self).tearDown()
 
     def test_get_window_type(self):
-        win = self.open_chrome_window("chrome://marionette/content/test.xul")
+        win = self.open_chrome_window("chrome://marionette/content/test.xhtml")
         self.marionette.switch_to_window(win)
 
         window_type = self.marionette.execute_script(
diff --git a/testing/marionette/harness/marionette_harness/tests/unit/unit-tests.ini b/testing/marionette/harness/marionette_harness/tests/unit/unit-tests.ini
index 1e8ce4bd92..13b4efa796 100644
--- a/testing/marionette/harness/marionette_harness/tests/unit/unit-tests.ini
+++ b/testing/marionette/harness/marionette_harness/tests/unit/unit-tests.ini
@@ -1,7 +1,7 @@
 [test_marionette.py]
 [test_transport.py]
 [test_cli_arguments.py]
-skip-if = manage_instance == false || appname == 'fennec' # Bug 1298921
+skip-if = manage_instance == false
 [test_geckoinstance.py]
 [test_data_driven.py]
 [test_session.py]
@@ -12,20 +12,15 @@ skip-if = manage_instance == false || appname == 'fennec' # Bug 1298921
 expected = fail
 [test_click.py]
 [test_click_chrome.py]
-skip-if = appname == 'fennec'
 [test_checkbox.py]
 [test_checkbox_chrome.py]
-skip-if = appname == 'fennec'
 [test_elementsize.py]
 [test_elementsize_chrome.py]
-skip-if = appname == 'fennec'
 [test_position.py]
 [test_rendered_element.py]
 [test_chrome_element_css.py]
-skip-if = appname == 'fennec'
 [test_element_state.py]
 [test_element_state_chrome.py]
-skip-if = appname == 'fennec'
 [test_text.py]
 
 [test_typing.py]
@@ -34,36 +29,26 @@ skip-if = appname == 'fennec'
 [test_execute_script.py]
 [test_element_retrieval.py]
 [test_findelement_chrome.py]
-skip-if = appname == 'fennec'
 
 [test_get_current_url_chrome.py]
 [test_navigation.py]
 [test_timeouts.py]
 
-[test_anonymous_content.py]
-skip-if = appname == 'fennec'
 [test_switch_frame.py]
 [test_switch_frame_chrome.py]
-skip-if = appname == 'fennec'
 [test_switch_window_chrome.py]
-skip-if = appname == 'fennec'
 [test_switch_window_content.py]
 
 [test_pagesource.py]
 [test_pagesource_chrome.py]
-skip-if = appname == 'fennec'
 
 [test_visibility.py]
 [test_window_handles_chrome.py]
-skip-if = appname == 'fennec'
 [test_window_handles_content.py]
 [test_window_close_chrome.py]
-skip-if = appname == 'fennec'
 [test_window_close_content.py]
 [test_window_rect.py]
-skip-if = appname == 'fennec'
 [test_window_maximize.py]
-skip-if = appname == 'fennec'
 [test_window_status_content.py]
 [test_window_status_chrome.py]
 
@@ -71,9 +56,7 @@ skip-if = appname == 'fennec'
 [test_cookies.py]
 [test_title.py]
 [test_title_chrome.py]
-skip-if = appname == 'fennec'
 [test_window_type_chrome.py]
-skip-if = appname == 'fennec'
 [test_implicit_waits.py]
 [test_wait.py]
 [test_expected.py]
@@ -84,40 +67,35 @@ skip-if = appname == 'fennec'
 [test_execute_isolate.py]
 [test_click_scrolling.py]
 [test_profile_management.py]
-skip-if = manage_instance == false || appname == 'fennec' || (debug && ((os == 'mac') || (os == 'linux'))) # Bug 1298921, Bug 1450355
+skip-if = manage_instance == false || (debug && ((os == 'mac') || (os == 'linux'))) # Bug 1450355
 [test_quit_restart.py]
-skip-if = manage_instance == false || appname == 'fennec' # Bug 1298921
+skip-if = manage_instance == false
 [test_context.py]
 
 [test_modal_dialogs.py]
-skip-if = appname == 'fennec' # Bug 1325738
 [test_unhandled_prompt_behavior.py]
-skip-if = appname == 'fennec' # Bug 1325738
 
 [test_key_actions.py]
 [test_mouse_action.py]
 
 [test_teardown_context_preserved.py]
 [test_file_upload.py]
-skip-if = appname == 'fennec' || os == "win" # http://bugs.python.org/issue14574
+skip-if = os == "win" # http://bugs.python.org/issue14574
 
 [test_execute_sandboxes.py]
 [test_prefs.py]
 [test_prefs_enforce.py]
-skip-if = manage_instance == false || appname == 'fennec' # Bug 1298921
+skip-if = manage_instance == false
 
 [test_shadow_dom.py]
 
 [test_chrome.py]
-skip-if = appname == 'fennec'
 
 [test_addons.py]
-skip-if = appname == 'fennec' # Bug 1330598
 
 [test_select.py]
 [test_crash.py]
-skip-if = asan || manage_instance == false || appname == 'fennec' # Bug 1298921
+skip-if = asan || manage_instance == false
 [test_localization.py]
 
 [test_reftest.py]
-skip-if = appname == 'fennec' # Bug 1519552
diff --git a/testing/marionette/interaction.js b/testing/marionette/interaction.js
index 0afe43d561..e25f89c4a6 100644
--- a/testing/marionette/interaction.js
+++ b/testing/marionette/interaction.js
@@ -63,7 +63,6 @@ const DISABLED_ATTRIBUTE_SUPPORTED_XUL = new Set([
   "SCALE",
   "TAB",
   "TABS",
-  "TEXTBOX",
   "TOOLBARBUTTON",
   "TREE",
 ]);
diff --git a/testing/marionette/jar.mn b/testing/marionette/jar.mn
index 87ac5bef4f..18003a3ad0 100644
--- a/testing/marionette/jar.mn
+++ b/testing/marionette/jar.mn
@@ -33,19 +33,18 @@ marionette.jar:
   content/prefs.js (prefs.js)
   content/proxy.js (proxy.js)
   content/reftest.js (reftest.js)
-  content/reftest.xul (reftest.xul)
+  content/reftest.xhtml (reftest.xhtml)
   content/server.js (server.js)
   content/stream-utils.js (stream-utils.js)
   content/sync.js (sync.js)
   content/transport.js (transport.js)
 #ifdef ENABLE_TESTS
-  content/test2.xul (chrome/test2.xul)
-  content/test_anonymous_content.xul (chrome/test_anonymous_content.xul)
+  content/test.xhtml (chrome/test.xhtml)
+  content/test2.xhtml (chrome/test2.xhtml)
   content/test_dialog.dtd (chrome/test_dialog.dtd)
   content/test_dialog.properties (chrome/test_dialog.properties)
-  content/test_dialog.xul (chrome/test_dialog.xul)
-  content/test_nested_iframe.xul (chrome/test_nested_iframe.xul)
-  content/test.xul (chrome/test.xul)
+  content/test_dialog.xhtml (chrome/test_dialog.xhtml)
+  content/test_nested_iframe.xhtml (chrome/test_nested_iframe.xhtml)
 #ifdef MOZ_CODE_COVERAGE
   content/PerTestCoverageUtils.jsm (../../tools/code-coverage/PerTestCoverageUtils.jsm)
 #endif
diff --git a/testing/marionette/listener.js b/testing/marionette/listener.js
index c210e3a6ea..e4af0412e4 100644
--- a/testing/marionette/listener.js
+++ b/testing/marionette/listener.js
@@ -1631,19 +1631,14 @@ function switchToFrame(msg) {
  *
  * Accepted values for |opts|:
  *
- *     @param {UUID=} id
- *         Optional web element reference of an element to take a screenshot
- *         of.
- *     @param {boolean=} full
- *         True to take a screenshot of the entire document element.  Is not
- *         considered if {@code id} is not defined.  Defaults to true.
- *     @param {Array.<UUID>=} highlights
- *         Draw a border around the elements found by their web element
- *         references.
- *     @param {boolean=} scroll
- *         When |id| is given, scroll it into view before taking the
- *         screenshot.  Defaults to true.
- *
+ * @param {UUID=} id
+ *     Optional web element reference of an element to take a screenshot of.
+ * @param {boolean=} full
+ *     True to take a screenshot of the entire document element. Is only
+ *     considered if <var>id</var> is not defined. Defaults to true.
+ * @param {boolean=} scroll
+ *     When <var>id</var> is given, scroll it into view before taking the
+ *     screenshot.  Defaults to true.
  * @param {capture.Format} format
  *     Format to return the screenshot in.
  * @param {Object.<string, ?>} opts
@@ -1652,25 +1647,13 @@ function switchToFrame(msg) {
  * @return {string}
  *     Base64 encoded string or a SHA-256 hash of the screenshot.
  */
-function takeScreenshot(format, opts = {}) {
-  let id = opts.id;
-  let full = !!opts.full;
-  let highlights = opts.highlights || [];
-  let scroll = !!opts.scroll;
-
+function takeScreenshot(format, { id, full = true, scroll = true } = {}) {
   let win = curContainer.frame;
 
   let canvas;
-  let highlightEls = highlights
-    .map(ref => WebElement.fromUUID(ref, "content"))
-    .map(webEl => seenEls.get(webEl, win));
 
-  // viewport
-  if (!id && !full) {
-    canvas = capture.viewport(win, highlightEls);
-
-    // element or full document element
-  } else {
+  // element or full document element
+  if (id || full) {
     let el;
     if (id) {
       let webEl = WebElement.fromUUID(id, "content");
@@ -1682,7 +1665,11 @@ function takeScreenshot(format, opts = {}) {
       el = win.document.documentElement;
     }
 
-    canvas = capture.element(el, highlightEls);
+    canvas = capture.element(el);
+
+    // viewport
+  } else {
+    canvas = capture.viewport(win);
   }
 
   switch (format) {
diff --git a/testing/marionette/modal.js b/testing/marionette/modal.js
index e9eba79d86..adcbdd7f39 100644
--- a/testing/marionette/modal.js
+++ b/testing/marionette/modal.js
@@ -8,7 +8,7 @@ const { Services } = ChromeUtils.import("resource://gre/modules/Services.jsm");
 
 this.EXPORTED_SYMBOLS = ["modal"];
 
-const COMMON_DIALOG = "chrome://global/content/commonDialog.xul";
+const COMMON_DIALOG = "chrome://global/content/commonDialog.xhtml";
 
 const isFirefox = () =>
   Services.appinfo.ID == "{ec8030f7-c20a-464f-9b0e-13a3a9e97384}";
diff --git a/testing/marionette/puppeteer/firefox/docs/ui/browser/tabbar.rst b/testing/marionette/puppeteer/firefox/docs/ui/browser/tabbar.rst
index 1ac431a991..4eebdb45fc 100644
--- a/testing/marionette/puppeteer/firefox/docs/ui/browser/tabbar.rst
+++ b/testing/marionette/puppeteer/firefox/docs/ui/browser/tabbar.rst
@@ -14,9 +14,3 @@ Tab
 
 .. autoclass:: Tab
    :members:
-
-MenuPanel
-----------
-
-.. autoclass:: MenuPanel
-   :members:
diff --git a/testing/marionette/puppeteer/firefox/firefox_puppeteer/ui/browser/notifications.py b/testing/marionette/puppeteer/firefox/firefox_puppeteer/ui/browser/notifications.py
index 5302aa62a4..abd2ed0b2b 100644
--- a/testing/marionette/puppeteer/firefox/firefox_puppeteer/ui/browser/notifications.py
+++ b/testing/marionette/puppeteer/firefox/firefox_puppeteer/ui/browser/notifications.py
@@ -65,8 +65,7 @@ class AddOnInstallBlockedNotification(BaseNotification):
         :returns: The allow button.
         """
         return self.element.find_element(
-            By.ANON_ATTRIBUTE, {'anonid': 'button'}).find_element(
-            By.ANON_ATTRIBUTE, {'anonid': 'button'})
+            By.CLASS, "popup-notification-primary-button")
 
 
 class AddOnInstallConfirmationNotification(BaseNotification):
diff --git a/testing/marionette/puppeteer/firefox/firefox_puppeteer/ui/browser/tabbar.py b/testing/marionette/puppeteer/firefox/firefox_puppeteer/ui/browser/tabbar.py
index 63ccce1ef7..446f154180 100644
--- a/testing/marionette/puppeteer/firefox/firefox_puppeteer/ui/browser/tabbar.py
+++ b/testing/marionette/puppeteer/firefox/firefox_puppeteer/ui/browser/tabbar.py
@@ -8,12 +8,10 @@ from marionette_driver import (
     By, Wait
 )
 
-from marionette_driver.errors import NoSuchElementException
-
 import firefox_puppeteer.errors as errors
 
 from firefox_puppeteer.api.security import Security
-from firefox_puppeteer.ui.base import UIBaseLib, DOMElement
+from firefox_puppeteer.ui.base import UIBaseLib
 
 
 class TabBar(UIBaseLib):
@@ -21,22 +19,13 @@ class TabBar(UIBaseLib):
 
     # Properties for visual elements of the tabs toolbar #
 
-    @property
-    def menupanel(self):
-        """A :class:`MenuPanel` instance which represents the menu panel
-        at the far right side of the tabs toolbar.
-
-        :returns: :class:`MenuPanel` instance.
-        """
-        return MenuPanel(self.marionette, self.window)
-
     @property
     def newtab_button(self):
         """The DOM element which represents the new tab button.
 
         :returns: Reference to the new tab button.
         """
-        return self.toolbar.find_element(By.ANON_ATTRIBUTE, {'anonid': 'tabs-newtab-button'})
+        return self.toolbar.find_element(By.ID, 'tabs-newtab-button')
 
     @property
     def tabs(self):
@@ -233,7 +222,7 @@ class Tab(UIBaseLib):
 
         :returns: Reference to the tab close button.
         """
-        return self.tab_element.find_element(By.ANON_ATTRIBUTE, {'anonid': 'close-button'})
+        return self.tab_element.find_element(By.CSS_SELECTOR, '.tab-close-button')
 
     @property
     def tab_element(self):
@@ -362,47 +351,3 @@ class Tab(UIBaseLib):
         Use the :func:`~Tab.select` method instead.
         """
         self.marionette.switch_to_window(self.handle)
-
-
-class MenuPanel(UIBaseLib):
-
-    @property
-    def popup(self):
-        """
-        :returns: The :class:`MenuPanelElement`.
-        """
-        popup = self.marionette.find_element(By.ID, 'PanelUI-popup')
-        return self.MenuPanelElement(popup)
-
-    class MenuPanelElement(DOMElement):
-        """Wraps the menu panel."""
-        _buttons = None
-
-        @property
-        def buttons(self):
-            """
-            :returns: A list of all the clickable buttons in the menu panel.
-            """
-            if not self._buttons:
-                self._buttons = (self.find_element(By.ID, 'PanelUI-multiView')
-                                     .find_element(By.ANON_ATTRIBUTE,
-                                                   {'anonid': 'viewContainer'})
-                                     .find_elements(By.TAG_NAME,
-                                                    'toolbarbutton'))
-            return self._buttons
-
-        def click(self, target=None):
-            """
-            Overrides HTMLElement.click to provide a target to click.
-
-            :param target: The label associated with the button to click on,
-             e.g., `New Private Window`.
-            """
-            if not target:
-                return DOMElement.click(self)
-
-            for button in self.buttons:
-                if button.get_attribute('label') == target:
-                    return button.click()
-            raise NoSuchElementException('Could not find "{}"" in the '
-                                         'menu panel UI'.format(target))
diff --git a/testing/marionette/puppeteer/firefox/firefox_puppeteer/ui/browser/toolbars.py b/testing/marionette/puppeteer/firefox/firefox_puppeteer/ui/browser/toolbars.py
index 2728b9afaf..9f3faa9ae0 100644
--- a/testing/marionette/puppeteer/firefox/firefox_puppeteer/ui/browser/toolbars.py
+++ b/testing/marionette/puppeteer/firefox/firefox_puppeteer/ui/browser/toolbars.py
@@ -79,7 +79,6 @@ class LocationBar(UIBaseLib):
     def __init__(self, *args, **kwargs):
         super(LocationBar, self).__init__(*args, **kwargs)
 
-        self._autocomplete_results = None
         self._identity_popup = None
 
     def clear(self):
@@ -90,29 +89,6 @@ class LocationBar(UIBaseLib):
             lambda _: self.value == '',
             message='Contents of location bar could not be cleared.')
 
-    def close_context_menu(self):
-        """Closes the Location Bar context menu by a key event."""
-        # TODO: This method should be implemented via the menu API.
-        self.contextmenu.send_keys(keys.Keys.ESCAPE)
-
-    @property
-    def connection_icon(self):
-        """ Provides access to the urlbar connection icon.
-
-        :returns: Reference to the connection icon element.
-        """
-        return self.marionette.find_element(By.ID, 'connection-icon')
-
-    @property
-    def contextmenu(self):
-        """Provides access to the urlbar context menu.
-
-        :returns: Reference to the urlbar context menu.
-        """
-        # TODO: This method should be implemented via the menu API.
-        parent = self.urlbar.find_element(By.ANON_ATTRIBUTE, {'anonid': 'moz-input-box'})
-        return parent.find_element(By.ANON_ATTRIBUTE, {'anonid': 'input-box-contextmenu'})
-
     @property
     def focused(self):
         """Checks the focus state of the location bar.
@@ -147,27 +123,6 @@ class LocationBar(UIBaseLib):
             lambda _: self.focused,
             message='Location bar has not be focused.')
 
-    def get_contextmenu_entry(self, action):
-        """Retrieves the urlbar context menu entry corresponding
-        to the given action.
-
-        :param action: The action corresponding to the retrieved value.
-        :returns: Reference to the urlbar contextmenu entry.
-        """
-        # TODO: This method should be implemented via the menu API.
-        entries = self.contextmenu.find_elements(By.CSS_SELECTOR, 'menuitem')
-        filter_on = 'cmd_%s' % action
-        found = [e for e in entries if e.get_attribute('cmd') == filter_on]
-        return found[0] if len(found) else None
-
-    @property
-    def history_drop_marker(self):
-        """Provides access to the history drop marker.
-
-        :returns: Reference to the history drop marker.
-        """
-        return self.urlbar.find_element(By.ANON_ATTRIBUTE, {'anonid': 'historydropmarker'})
-
     @property
     def identity_box(self):
         """The DOM element which represents the identity box.
@@ -279,7 +234,7 @@ class LocationBar(UIBaseLib):
 
         :returns: Reference to the urlbar input.
         """
-        return self.urlbar.find_element(By.ANON_ATTRIBUTE, {'anonid': 'input'})
+        return self.marionette.find_element(By.ID, 'urlbar-input')
 
     @property
     def value(self):
@@ -287,113 +242,7 @@ class LocationBar(UIBaseLib):
 
         :returns: The urlbar value.
         """
-        return self.urlbar.get_property('value')
-
-
-class AutocompleteResults(UIBaseLib):
-    """Wraps DOM elements and methods for interacting with autocomplete results."""
-
-    def close(self, force=False):
-        """Closes the urlbar autocomplete popup.
-
-        :param force: If true, the popup is closed by its own hide function,
-                      otherwise a key event is sent to close the popup.
-        """
-        if not self.is_open:
-            return
-
-        if force:
-            self.marionette.execute_script("""
-              arguments[0].hidePopup();
-            """, script_args=[self.element])
-        else:
-            self.element.send_keys(keys.Keys.ESCAPE)
-
-        Wait(self.marionette).until(
-            lambda _: not self.is_open,
-            message='Autocomplete popup has not been closed.')
-
-    def get_matching_text(self, result, match_type):
-        """Returns an array of strings of the matching text within an autocomplete
-        result in the urlbar.
-
-        :param result: The result to inspect for matches.
-        :param match_type: The type of match to search for (one of `title` or `url`).
-        """
-
-        if match_type not in ('title', 'url'):
-            raise ValueError('match_type provided must be one of'
-                             '"title" or "url", not %s' % match_type)
-
-        # Search for nodes of the given type with emphasized text
-        emphasized_nodes = result.find_elements(
-            By.ANON_ATTRIBUTE,
-            {'class': 'ac-emphasize-text ac-emphasize-text-%s' % match_type}
-        )
-
-        return [node.get_property('textContent') for node in emphasized_nodes]
-
-    @property
-    def visible_results(self):
-        """Supplies the list of visible autocomplete result nodes.
-
-        :returns: The list of visible results.
-        """
-        match_count = self.element.get_property('matchCount')
-
-        return self.marionette.execute_script("""
-          let rv = [];
-          let node = arguments[0];
-          let count = arguments[1];
-
-          for (let i = 0; i < count; ++i) {
-            rv.push(node.getItemAtIndex(i));
-          }
-
-          return rv;
-        """, script_args=[self.results, match_count])
-
-    @property
-    def is_open(self):
-        """Returns whether this popup is currently open.
-
-        :returns: True when the popup is open, otherwise false.
-        """
-        return self.element.get_property('state') == 'open'
-
-    @property
-    def is_complete(self):
-        """Returns when this popup is open and autocomplete results are complete.
-
-        :returns: True, when autocomplete results have been populated.
-        """
-        return self.marionette.execute_script("""
-          Components.utils.import("resource://gre/modules/Services.jsm");
-
-          let win = Services.focus.activeWindow;
-          if (win) {
-            return win.gURLBar.controller.searchStatus >=
-                   Components.interfaces.nsIAutoCompleteController.STATUS_COMPLETE_NO_MATCH;
-          }
-
-          return null;
-        """)
-
-    @property
-    def results(self):
-        """
-        :returns: The autocomplete result container node.
-        """
-        return self.element.find_element(By.ANON_ATTRIBUTE,
-                                         {'anonid': 'richlistbox'})
-
-    @property
-    def selected_index(self):
-        """Provides the index of the selected item in the autocomplete list.
-
-        :returns: The index.
-        """
-        return self.results.get_property('selectedIndex')
+        return self.urlbar_input.get_property('value')
 
 
 class IdentityPopup(UIBaseLib):
diff --git a/testing/marionette/puppeteer/firefox/firefox_puppeteer/ui/browser/window.py b/testing/marionette/puppeteer/firefox/firefox_puppeteer/ui/browser/window.py
index e9dd33c589..930c5e683f 100644
--- a/testing/marionette/puppeteer/firefox/firefox_puppeteer/ui/browser/window.py
+++ b/testing/marionette/puppeteer/firefox/firefox_puppeteer/ui/browser/window.py
@@ -35,7 +35,6 @@ class BrowserWindow(BaseWindow):
     properties = [
         'chrome://branding/locale/brand.properties',
         'chrome://browser/locale/browser.properties',
-        'chrome://browser/locale/preferences/preferences.properties',
         'chrome://global/locale/browser.properties',
     ]
 
diff --git a/testing/marionette/puppeteer/firefox/firefox_puppeteer/ui/update_wizard/wizard.py b/testing/marionette/puppeteer/firefox/firefox_puppeteer/ui/update_wizard/wizard.py
index cc1215078a..afacc8e95d 100644
--- a/testing/marionette/puppeteer/firefox/firefox_puppeteer/ui/update_wizard/wizard.py
+++ b/testing/marionette/puppeteer/firefox/firefox_puppeteer/ui/update_wizard/wizard.py
@@ -50,7 +50,7 @@ class Wizard(UIBaseLib):
 
     @property
     def _buttons(self):
-        return self.element.find_element(By.ANON_ATTRIBUTE, {'anonid': 'Buttons'})
+        return self.element.get_property('_wizardButtons')
 
     @property
     def cancel_button(self):
diff --git a/testing/marionette/reftest.js b/testing/marionette/reftest.js
index 820865e03e..9b2e18c430 100644
--- a/testing/marionette/reftest.js
+++ b/testing/marionette/reftest.js
@@ -137,7 +137,7 @@ reftest.Runner = class {
     assert.positiveInteger(height);
 
     let reftestWin = this.parentWindow.open(
-      "chrome://marionette/content/reftest.xul",
+      "chrome://marionette/content/reftest.xhtml",
       "reftest",
       `chrome,height=${height},width=${width}`
     );
@@ -157,7 +157,6 @@ reftest.Runner = class {
       browser = reftestWin.document.createElementNS(XUL_NS, "xul:browser");
       browser.permanentKey = {};
       browser.setAttribute("id", "browser");
-      browser.setAttribute("anonid", "initialBrowser");
       browser.setAttribute("type", "content");
       browser.setAttribute("primary", "true");
       if (this.remote) {
diff --git a/testing/marionette/reftest.xul b/testing/marionette/reftest.xhtml
similarity index 100%
rename from testing/marionette/reftest.xul
rename to testing/marionette/reftest.xhtml
diff --git a/testing/mochitest/BrowserTestUtils/BrowserTestUtils.jsm b/testing/mochitest/BrowserTestUtils/BrowserTestUtils.jsm
index 85093ab7c1..7a444eedcc 100644
--- a/testing/mochitest/BrowserTestUtils/BrowserTestUtils.jsm
+++ b/testing/mochitest/BrowserTestUtils/BrowserTestUtils.jsm
@@ -780,7 +780,7 @@ var BrowserTestUtils = {
     return new Promise(resolve => {
       async function observer(subject, topic, data) {
         if (topic == "domwindowopened" && (!win || subject === win)) {
-          let observedWindow = subject.QueryInterface(Ci.nsIDOMWindow);
+          let observedWindow = subject;
           if (checkFn && !(await checkFn(observedWindow))) {
             return;
           }
@@ -806,7 +806,7 @@ var BrowserTestUtils = {
       function observer(subject, topic, data) {
         if (topic == "domwindowclosed" && (!win || subject === win)) {
           Services.ww.unregisterNotification(observer);
-          resolve(subject.QueryInterface(Ci.nsIDOMWindow));
+          resolve(subject);
         }
       }
       Services.ww.registerNotification(observer);
@@ -2123,7 +2123,7 @@ var BrowserTestUtils = {
    */
   async promiseAlertDialogOpen(
     buttonAction,
-    uri = "chrome://global/content/commonDialog.xul",
+    uri = "chrome://global/content/commonDialog.xhtml",
     func
   ) {
     let win = await this.domWindowOpened(null, async win => {
@@ -2140,8 +2140,8 @@ var BrowserTestUtils = {
       return win;
     }
 
-    let doc = win.document.documentElement;
-    doc.getButton(buttonAction).click();
+    let dialog = win.document.querySelector("dialog");
+    dialog.getButton(buttonAction).click();
 
     return win;
   },
@@ -2161,7 +2161,7 @@ var BrowserTestUtils = {
    */
   async promiseAlertDialog(
     buttonAction,
-    uri = "chrome://global/content/commonDialog.xul",
+    uri = "chrome://global/content/commonDialog.xhtml",
     func
   ) {
     let win = await this.promiseAlertDialogOpen(buttonAction, uri, func);
diff --git a/testing/mochitest/baselinecoverage/chrome/chrome.ini b/testing/mochitest/baselinecoverage/chrome/chrome.ini
index 9c9f736026..4f427ca9e2 100644
--- a/testing/mochitest/baselinecoverage/chrome/chrome.ini
+++ b/testing/mochitest/baselinecoverage/chrome/chrome.ini
@@ -1,4 +1,4 @@
 [DEFAULT]
 
-[test_baselinecoverage.xul]
+[test_baselinecoverage.xhtml]
 run-if = ccov && verify
\ No newline at end of file
diff --git a/testing/mochitest/baselinecoverage/chrome/test_baselinecoverage.xul b/testing/mochitest/baselinecoverage/chrome/test_baselinecoverage.xhtml
similarity index 100%
rename from testing/mochitest/baselinecoverage/chrome/test_baselinecoverage.xul
rename to testing/mochitest/baselinecoverage/chrome/test_baselinecoverage.xhtml
diff --git a/testing/mochitest/browser-harness.xul b/testing/mochitest/browser-harness.xhtml
similarity index 99%
rename from testing/mochitest/browser-harness.xul
rename to testing/mochitest/browser-harness.xhtml
index 99e6fd6ebe..8b71800f28 100644
--- a/testing/mochitest/browser-harness.xul
+++ b/testing/mochitest/browser-harness.xhtml
@@ -72,7 +72,7 @@
           try {
             logger = new MozillaFileLogger(gConfig.logFile)
           } catch (ex) {
-            dump("TEST-UNEXPECTED-FAIL | (browser-harness.xul) | " +
+            dump("TEST-UNEXPECTED-FAIL | (browser-harness.xhtml) | " +
                  "Error trying to log to " + gConfig.logFile + ": " + ex + "\n");
           }
         }
diff --git a/testing/mochitest/browser-test.js b/testing/mochitest/browser-test.js
index 4a442b86d5..33902d3c96 100644
--- a/testing/mochitest/browser-test.js
+++ b/testing/mochitest/browser-test.js
@@ -5,7 +5,6 @@
 // Test timeout (seconds)
 var gTimeoutSeconds = 45;
 var gConfig;
-var gSaveInstrumentationData = null;
 
 var { AppConstants } = ChromeUtils.import(
   "resource://gre/modules/AppConstants.jsm"
@@ -96,7 +95,7 @@ function testInit() {
 
     Services.ww.openWindow(
       window,
-      "chrome://mochikit/content/browser-harness.xul",
+      "chrome://mochikit/content/browser-harness.xhtml",
       "browserTest",
       "chrome,centerscreen,dialog=no,resizable,titlebar,toolbar=no,width=800,height=600",
       sstring
@@ -148,279 +147,6 @@ function testInit() {
     "chrome://mochikit/content/tests/SimpleTest/AsyncUtilsContent.js",
     true
   );
-
-  var testSuite = Cc["@mozilla.org/process/environment;1"]
-    .getService(Ci.nsIEnvironment)
-    .get("TEST_SUITE");
-  if (testSuite == "browser-chrome-instrumentation") {
-    takeInstrumentation();
-  }
-}
-
-function takeInstrumentation() {
-  let instrumentData = {
-    elements: {},
-  };
-
-  function pad(str, length) {
-    if (str.length >= length) {
-      return str;
-    }
-
-    return str + " ".repeat(length - str.length);
-  }
-
-  function byCount(a, b) {
-    return b[1] - a[1];
-  }
-
-  function getSummaryText() {
-    let summary = [];
-    let allData = {};
-    for (let selector of Object.keys(instrumentData.elements)) {
-      allData[selector] = instrumentData.elements[selector];
-    }
-
-    let selectors = Object.keys(allData);
-    let elements = selectors.map(s => allData[s]);
-
-    let namespaceMap = new Map();
-    let bindingMap = new Map();
-
-    for (let element of elements) {
-      if (!bindingMap.has(element.binding)) {
-        bindingMap.set(element.binding, 1);
-      } else {
-        bindingMap.set(element.binding, bindingMap.get(element.binding) + 1);
-      }
-
-      if (!namespaceMap.has(element.namespaceURI)) {
-        namespaceMap.set(element.namespaceURI, new Map());
-      }
-
-      let localNameMap = namespaceMap.get(element.namespaceURI);
-      if (!localNameMap.has(element.localName)) {
-        localNameMap.set(element.localName, 1);
-      } else {
-        localNameMap.set(
-          element.localName,
-          localNameMap.get(element.localName) + 1
-        );
-      }
-    }
-
-    for (let [namespace, localNameMap] of namespaceMap) {
-      summary.push(`Elements in namespace ${namespace}`);
-
-      let entries = Array.from(localNameMap);
-      entries.sort(byCount);
-      for (let entry of entries) {
-        summary.push(`  ${pad(entry[1] + "", 5)} ${entry[0]}`);
-      }
-    }
-
-    summary.push("XBL bindings");
-    let bindings = Array.from(bindingMap);
-    bindings.sort(byCount);
-    let bindingsJSON = {};
-    for (let binding of bindings) {
-      summary.push(`  ${pad(binding[1] + "", 5)} ${binding[0]}`);
-      if (binding[0]) {
-        bindingsJSON[binding[0].split("#")[1].split('"')[0]] = binding[1];
-      }
-    }
-
-    summary.push("XBL bindings as JSON");
-    summary.push(JSON.stringify(bindingsJSON, null, 2));
-
-    return summary.join("\n");
-  }
-
-  // Saves instrumantation data
-  function saveData() {
-    let path = Cc["@mozilla.org/process/environment;1"]
-      .getService(Ci.nsIEnvironment)
-      .get("MOZ_UPLOAD_DIR");
-    let encoder = new TextEncoder();
-
-    let instrumentPath = OS.Path.join(path, "xulinstrument.txt");
-    OS.File.writeAtomic(
-      instrumentPath,
-      encoder.encode(JSON.stringify(instrumentData, null, 2))
-    );
-
-    let summaryPath = OS.Path.join(path, "xulsummary.txt");
-    OS.File.writeAtomic(summaryPath, encoder.encode(getSummaryText()));
-  }
-
-  // An iterator over an element and its ancestors
-  function* elementPath(element) {
-    yield element;
-    while ((element = element.parentNode) && element instanceof Element) {
-      yield element;
-    }
-  }
-
-  // Returns the information we care about for an element
-  function getElementInfo(element) {
-    let style = element.ownerGlobal.getComputedStyle(element);
-    let binding = style && style.getPropertyValue("-moz-binding");
-
-    return {
-      namespaceURI: element.namespaceURI,
-      localName: element.localName,
-      binding: binding && binding != "none" ? binding : null,
-    };
-  }
-
-  // The selector for just this element
-  function immediateSelector(element) {
-    if (
-      element.localName == "notificationbox" &&
-      element.parentNode &&
-      element.parentNode.id == "tabbrowser-tabpanels"
-    ) {
-      // Don't do a full selector for a tabpanel's notificationbox
-      return element.localName;
-    }
-
-    if (
-      element.localName == "tab" &&
-      element.classList.contains("tabbrowser-tab")
-    ) {
-      // Don't do a full selector for a tab
-      return element.localName;
-    }
-
-    if (element.id) {
-      return `#${element.id}`;
-    }
-
-    let selector = element.localName;
-
-    if (element.classList.length) {
-      selector += `.${Array.from(element.classList).join(".")}`;
-    }
-
-    for (let attr of ["src", "label"]) {
-      if (element.hasAttribute(attr)) {
-        selector += `[${attr}=${JSON.stringify(element.getAttribute(attr))}]`;
-      }
-    }
-
-    return selector;
-  }
-
-  // The selector chain for the element
-  function elementSelector(element) {
-    return Array.from(elementPath(element))
-      .reverse()
-      .map(immediateSelector)
-      .join(" > ");
-  }
-
-  // An iterator over all elements in the window
-  function* windowElements(win) {
-    yield* elementDescendants(win.document.documentElement);
-  }
-
-  // An iterator over an element and all of its descendants
-  function* elementDescendants(element) {
-    let walker = Cc["@mozilla.org/inspector/deep-tree-walker;1"].createInstance(
-      Ci.inIDeepTreeWalker
-    );
-    walker.showAnonymousContent = true;
-    walker.showSubDocuments = false;
-    walker.showDocumentsAsNodes = false;
-    walker.init(element, NodeFilter.SHOW_ELEMENT);
-
-    yield element;
-    while (walker.nextNode()) {
-      if (walker.currentNode instanceof Element) {
-        yield walker.currentNode;
-      }
-    }
-  }
-
-  // Checks if we've seen an element and if not adds it to the instrumentation data
-  function instrumentElement(element) {
-    if (element.__instrumentSeen) {
-      return;
-    }
-
-    let selector = elementSelector(element);
-    element.__instrumentSeen = true;
-
-    if (selector in instrumentData.elements) {
-      return;
-    }
-
-    instrumentData.elements[selector] = getElementInfo(element);
-  }
-
-  // Instruments every element in a window
-  function scanWindow(win) {
-    Array.from(windowElements(win)).forEach(instrumentElement);
-  }
-
-  // Instruments every element in an element's descendants
-  function scanElement(element) {
-    Array.from(elementDescendants(element)).forEach(instrumentElement);
-  }
-
-  function handleMutation(mutation) {
-    if (mutation.type != "childList") {
-      return;
-    }
-
-    for (let node of mutation.addedNodes) {
-      if (node instanceof Element) {
-        scanElement(node);
-      }
-    }
-  }
-  // Watches a window for new elements to instrument
-  function observeWindow(win) {
-    let observer = new MutationObserver(mutations => {
-      mutations.forEach(handleMutation);
-    });
-
-    observer.observe(win.document, {
-      childList: true,
-      subtree: true,
-    });
-
-    win.addEventListener(
-      "unload",
-      () => {
-        observer.takeRecords().forEach(handleMutation);
-      },
-      { once: true }
-    );
-  }
-
-  scanWindow(window);
-  observeWindow(window);
-  gSaveInstrumentationData = saveData;
-
-  Services.ww.registerNotification((win, topic, data) => {
-    if (topic != "domwindowopened") {
-      return;
-    }
-
-    win.addEventListener(
-      "load",
-      () => {
-        if (win.location.href != AppConstants.BROWSER_CHROME_URL) {
-          return;
-        }
-
-        scanWindow(win);
-        observeWindow(win);
-      },
-      { once: true }
-    );
-  });
 }
 
 function isGenerator(value) {
@@ -637,11 +363,8 @@ Tester.prototype = {
   },
 
   async promiseMainWindowReady() {
-    if (window.gBrowserInit && !gBrowserInit.idleTasksFinished) {
-      await this.TestUtils.topicObserved(
-        "browser-idle-startup-tasks-finished",
-        subject => subject === window
-      );
+    if (window.gBrowserInit) {
+      await window.gBrowserInit.idleTasksFinishedPromise;
     }
   },
 
@@ -680,7 +403,7 @@ Tester.prototype = {
     // Remove stale tabs
     if (this.currentTest && window.gBrowser && gBrowser.tabs.length > 1) {
       while (gBrowser.tabs.length > 1) {
-        let lastTab = gBrowser.tabContainer.lastElementChild;
+        let lastTab = gBrowser.tabs[gBrowser.tabs.length - 1];
         if (!lastTab.closing) {
           // Report the stale tab as an error only when they're not closing.
           // Tests can finish without waiting for the closing tabs.
@@ -793,10 +516,6 @@ Tester.prototype = {
     this.callback(this.tests);
     this.callback = null;
     this.tests = null;
-
-    if (gSaveInstrumentationData) {
-      gSaveInstrumentationData();
-    }
   },
 
   haltTests: function Tester_haltTests() {
diff --git a/testing/mochitest/chrome/chrome.ini b/testing/mochitest/chrome/chrome.ini
index 95c355b56b..3229f33e02 100644
--- a/testing/mochitest/chrome/chrome.ini
+++ b/testing/mochitest/chrome/chrome.ini
@@ -2,15 +2,15 @@
 skip-if = os == 'android'
 support-files = test-dir/test-file
 
-[test_sample.xul]
-[test_sanityEventUtils.xul]
+[test_sample.xhtml]
+[test_sanityEventUtils.xhtml]
 [test_sanityPluginUtils.html]
-[test_sanityException.xul]
-[test_sanityException2.xul]
-[test_sanityManifest.xul]
+[test_sanityException.xhtml]
+[test_sanityException2.xhtml]
+[test_sanityManifest.xhtml]
 fail-if = true
-[test_sanityManifest_pf.xul]
+[test_sanityManifest_pf.xhtml]
 fail-if = true
-[test_chromeGetTestFile.xul]
-[test_tasks_skip.xul]
-[test_tasks_skipall.xul]
+[test_chromeGetTestFile.xhtml]
+[test_tasks_skip.xhtml]
+[test_tasks_skipall.xhtml]
diff --git a/testing/mochitest/chrome/test_chromeGetTestFile.xul b/testing/mochitest/chrome/test_chromeGetTestFile.xhtml
similarity index 93%
rename from testing/mochitest/chrome/test_chromeGetTestFile.xul
rename to testing/mochitest/chrome/test_chromeGetTestFile.xhtml
index 37fc79622b..8654a7d373 100644
--- a/testing/mochitest/chrome/test_chromeGetTestFile.xul
+++ b/testing/mochitest/chrome/test_chromeGetTestFile.xhtml
@@ -17,21 +17,21 @@
     SimpleTest.waitForExplicitFinish();
 
     SimpleTest.doesThrow(function () {
-      getTestFilePath("/test_chromeGetTestFile.xul")
+      getTestFilePath("/test_chromeGetTestFile.xhtml")
     }, "getTestFilePath rejects absolute paths");
 
     Promise.all([
-      OS.File.exists(getTestFilePath("test_chromeGetTestFile.xul"))
+      OS.File.exists(getTestFilePath("test_chromeGetTestFile.xhtml"))
         .then(function (exists) {
           ok(exists, "getTestFilePath consider the path as being relative");
         }),
 
-      OS.File.exists(getTestFilePath("./test_chromeGetTestFile.xul"))
+      OS.File.exists(getTestFilePath("./test_chromeGetTestFile.xhtml"))
         .then(function (exists) {
           ok(exists, "getTestFilePath also accepts explicit relative path");
         }),
 
-      OS.File.exists(getTestFilePath("./test_chromeGetTestFileTypo.xul"))
+      OS.File.exists(getTestFilePath("./test_chromeGetTestFileTypo.xhtml"))
         .then(function (exists) {
           ok(!exists, "getTestFilePath do not throw if the file doesn't exists");
         }),
diff --git a/testing/mochitest/chrome/test_sample.xul b/testing/mochitest/chrome/test_sample.xhtml
similarity index 100%
rename from testing/mochitest/chrome/test_sample.xul
rename to testing/mochitest/chrome/test_sample.xhtml
diff --git a/testing/mochitest/chrome/test_sanityEventUtils.xul b/testing/mochitest/chrome/test_sanityEventUtils.xhtml
similarity index 85%
rename from testing/mochitest/chrome/test_sanityEventUtils.xul
rename to testing/mochitest/chrome/test_sanityEventUtils.xhtml
index 19fe1ab422..6521386852 100644
--- a/testing/mochitest/chrome/test_sanityEventUtils.xul
+++ b/testing/mochitest/chrome/test_sanityEventUtils.xhtml
@@ -106,24 +106,6 @@
       var startTime = new Date();
       var result;
 
-      /* test synthesizeDragStart */
-      result = synthesizeDragStart($("drag1"), drag1, window);
-      is(result, null, "drag1 is text/uri-list");
-      result = synthesizeDragStart($("drag1"), drag1WrongFlavor, window);
-      isnot(result, null, "drag1 is not text/plain");
-      result = synthesizeDragStart($("drag1"), drag2items, window);
-      isnot(result, null, "drag1 is not 2 items");
-      result = synthesizeDragStart($("drag2"), drag2, window);
-      is(result, null, "drag2 is ordered text/plain then text/uri-list");
-      result = synthesizeDragStart($("drag2"), drag1, window);
-      isnot(result, null, "drag2 is not one flavor");
-      result = synthesizeDragStart($("drag2"), drag2WrongOrder, window);
-      isnot(result, null, "drag2 is not ordered text/uri-list then text/plain");
-      result = synthesizeDragStart($("dragfile"), dragfile, window);
-      is(result, null, "dragfile is nsIFile");
-      result = synthesizeDragStart($("drag1"), null, window);
-      is(result, regularDtForDrag1, "synthesizeDragStart accepts null expectedDragData");
-     
       /* test synthesizeDrop */
       result = synthesizeDrop($("dragDrop"), $("dragDrop"), dragDrop, null, window);
       ok(gEnter, "Fired dragenter");
diff --git a/testing/mochitest/chrome/test_sanityException.xul b/testing/mochitest/chrome/test_sanityException.xhtml
similarity index 100%
rename from testing/mochitest/chrome/test_sanityException.xul
rename to testing/mochitest/chrome/test_sanityException.xhtml
diff --git a/testing/mochitest/chrome/test_sanityException2.xul b/testing/mochitest/chrome/test_sanityException2.xhtml
similarity index 100%
rename from testing/mochitest/chrome/test_sanityException2.xul
rename to testing/mochitest/chrome/test_sanityException2.xhtml
diff --git a/testing/mochitest/chrome/test_sanityManifest.xul b/testing/mochitest/chrome/test_sanityManifest.xhtml
similarity index 100%
rename from testing/mochitest/chrome/test_sanityManifest.xul
rename to testing/mochitest/chrome/test_sanityManifest.xhtml
diff --git a/testing/mochitest/chrome/test_sanityManifest_pf.xul b/testing/mochitest/chrome/test_sanityManifest_pf.xhtml
similarity index 100%
rename from testing/mochitest/chrome/test_sanityManifest_pf.xul
rename to testing/mochitest/chrome/test_sanityManifest_pf.xhtml
diff --git a/testing/mochitest/chrome/test_tasks_skip.xul b/testing/mochitest/chrome/test_tasks_skip.xhtml
similarity index 100%
rename from testing/mochitest/chrome/test_tasks_skip.xul
rename to testing/mochitest/chrome/test_tasks_skip.xhtml
diff --git a/testing/mochitest/chrome/test_tasks_skipall.xul b/testing/mochitest/chrome/test_tasks_skipall.xhtml
similarity index 100%
rename from testing/mochitest/chrome/test_tasks_skipall.xul
rename to testing/mochitest/chrome/test_tasks_skipall.xhtml
diff --git a/testing/mochitest/harness.xul b/testing/mochitest/harness.xhtml
similarity index 100%
rename from testing/mochitest/harness.xul
rename to testing/mochitest/harness.xhtml
diff --git a/testing/mochitest/leaks.py b/testing/mochitest/leaks.py
index 225ec0f223..da4c472e4c 100644
--- a/testing/mochitest/leaks.py
+++ b/testing/mochitest/leaks.py
@@ -189,7 +189,7 @@ class ShutdownLeaks(object):
 
     def _isHiddenWindowURL(self, url):
         return (url == "resource://gre-resources/hiddenWindow.html" or  # Win / Linux
-                url == "chrome://browser/content/hiddenWindow.xul")     # Mac
+                url == "chrome://browser/content/hiddenWindowMac.xhtml")     # Mac
 
 
 class LSANLeaks(object):
diff --git a/testing/mochitest/mochitest_options.py b/testing/mochitest/mochitest_options.py
index 99081f8ae4..c63fdda330 100644
--- a/testing/mochitest/mochitest_options.py
+++ b/testing/mochitest/mochitest_options.py
@@ -539,12 +539,6 @@ class MochitestArguments(ArgumentContainer):
           "help": "Filter out tests that don't have the given tag. Can be used multiple "
                   "times in which case the test must contain at least one of the given tags.",
           }],
-        [["--enable-cpow-warnings"],
-         {"action": "store_true",
-          "dest": "enableCPOWWarnings",
-          "help": "Enable logging of unsafe CPOW usage, which is disabled by default for tests",
-          "suppress": True,
-          }],
         [["--marionette"],
          {"default": None,
           "help": "host:port to use when connecting to Marionette",
diff --git a/testing/mochitest/moz.build b/testing/mochitest/moz.build
index 6dd34b600f..9956433301 100644
--- a/testing/mochitest/moz.build
+++ b/testing/mochitest/moz.build
@@ -20,11 +20,11 @@ FINAL_TARGET_FILES += [
 ]
 
 FINAL_TARGET_FILES.content += [
-    'browser-harness.xul',
+    'browser-harness.xhtml',
     'browser-test.js',
     'chrome-harness.js',
     'chunkifyTests.js',
-    'harness.xul',
+    'harness.xhtml',
     'manifestLibrary.js',
     'mochitest-e10s-utils.js',
     'nested_setup.js',
@@ -94,12 +94,12 @@ TEST_HARNESS_FILES.testing.mochitest += [
     '/build/valgrind/x86_64-pc-linux-gnu.sup',
     '/netwerk/test/httpserver/httpd.js',
     'bisection.py',
-    'browser-harness.xul',
+    'browser-harness.xhtml',
     'browser-test.js',
     'chrome-harness.js',
     'chunkifyTests.js',
     'favicon.ico',
-    'harness.xul',
+    'harness.xhtml',
     'leaks.py',
     'mach_test_package_commands.py',
     'manifest.webapp',
diff --git a/testing/mochitest/redirect.html b/testing/mochitest/redirect.html
index 17f60e3952..1536ed4e38 100644
--- a/testing/mochitest/redirect.html
+++ b/testing/mochitest/redirect.html
@@ -17,7 +17,7 @@
     }
 
     function redirectToHarness() {
-      redirect("chrome://mochikit/content/harness.xul");
+      redirect("chrome://mochikit/content/harness.xhtml");
     }
 
     function onLoad() {
diff --git a/testing/mochitest/tests/Harness_sanity/test_SpecialPowersExtension.html b/testing/mochitest/tests/Harness_sanity/test_SpecialPowersExtension.html
index c61c0a785e..764e0ef864 100644
--- a/testing/mochitest/tests/Harness_sanity/test_SpecialPowersExtension.html
+++ b/testing/mochitest/tests/Harness_sanity/test_SpecialPowersExtension.html
@@ -81,9 +81,15 @@ function starttest(){
   
   // QueryInterface and getPrivilegedProps tests
   is(SpecialPowers.can_QI(SpecialPowers), false);
-  ok(SpecialPowers.can_QI(window));
-  ok(SpecialPowers.do_QueryInterface(window, "nsIDOMWindow"));
-  is(SpecialPowers.getPrivilegedProps(SpecialPowers.do_QueryInterface(window, "nsIDOMWindow"), "document.nodeName"), "#document");
+  let doc = SpecialPowers.wrap(document);
+  is(SpecialPowers.getPrivilegedProps(doc, "baseURIObject.fileName"), null,
+     "Should not have a fileName property yet");
+  let uri = SpecialPowers.getPrivilegedProps(doc, "baseURIObject");
+  ok(SpecialPowers.can_QI(uri));
+  ok(SpecialPowers.do_QueryInterface(uri, "nsIURL"));
+  is(SpecialPowers.getPrivilegedProps(doc, "baseURIObject.fileName"),
+     "test_SpecialPowersExtension.html",
+     "Should have a fileName property now");
   
   //try to run garbage collection
   SpecialPowers.gc();
diff --git a/testing/mochitest/tests/SimpleTest/EventUtils.js b/testing/mochitest/tests/SimpleTest/EventUtils.js
index 4420876a62..b7211c5719 100644
--- a/testing/mochitest/tests/SimpleTest/EventUtils.js
+++ b/testing/mochitest/tests/SimpleTest/EventUtils.js
@@ -21,6 +21,7 @@
  *  synthesizeDropAfterDragOver
  *  synthesizeDrop
  *  synthesizePlainDragAndDrop
+ *  synthesizePlainDragAndCancel
  *
  *  When adding methods to this file, please add a performance test for it.
  */
@@ -34,25 +35,28 @@
 // placebo for compat. An easy way to differentiate this from the real thing
 // is whether the property is read-only or not.  The real |Components| property
 // is read-only.
-window.__defineGetter__('_EU_Ci', function() {
-  var c = Object.getOwnPropertyDescriptor(window, 'Components');
+window.__defineGetter__("_EU_Ci", function() {
+  var c = Object.getOwnPropertyDescriptor(window, "Components");
   return c && c.value && !c.writable ? Ci : SpecialPowers.Ci;
 });
 
-window.__defineGetter__('_EU_Cc', function() {
-  var c = Object.getOwnPropertyDescriptor(window, 'Components');
+window.__defineGetter__("_EU_Cc", function() {
+  var c = Object.getOwnPropertyDescriptor(window, "Components");
   return c && c.value && !c.writable ? Cc : SpecialPowers.Cc;
 });
 
-window.__defineGetter__('_EU_Cu', function() {
-  var c = Object.getOwnPropertyDescriptor(window, 'Components');
+window.__defineGetter__("_EU_Cu", function() {
+  var c = Object.getOwnPropertyDescriptor(window, "Components");
   return c && c.value && !c.writable ? Cu : SpecialPowers.Cu;
 });
 
 window.__defineGetter__("_EU_OS", function() {
   delete this._EU_OS;
   try {
-    this._EU_OS = this._EU_Cu.import("resource://gre/modules/AppConstants.jsm", {}).platform;
+    this._EU_OS = this._EU_Cu.import(
+      "resource://gre/modules/AppConstants.jsm",
+      {}
+    ).platform;
   } catch (ex) {
     this._EU_OS = null;
   }
@@ -121,12 +125,12 @@ function _EU_maybeWrap(o) {
     // Not much we can do here.
     return o;
   }
-  var c = Object.getOwnPropertyDescriptor(window, 'Components');
+  var c = Object.getOwnPropertyDescriptor(window, "Components");
   return c && c.value && !c.writable ? o : SpecialPowers.wrap(o);
 }
 
 function _EU_maybeUnwrap(o) {
-  var c = Object.getOwnPropertyDescriptor(window, 'Components');
+  var c = Object.getOwnPropertyDescriptor(window, "Components");
   return c && c.value && !c.writable ? o : SpecialPowers.unwrap(o);
 }
 
@@ -140,23 +144,33 @@ function _EU_maybeUnwrap(o) {
  * sendMouseEvent({type:'click'}, 'node');
  */
 function getElement(id) {
-  return ((typeof(id) == "string") ?
-    document.getElementById(id) : id); 
-};   
+  return typeof id == "string" ? document.getElementById(id) : id;
+}
 
 this.$ = this.getElement;
 
 function computeButton(aEvent) {
-  if (typeof aEvent.button != 'undefined') {
+  if (typeof aEvent.button != "undefined") {
     return aEvent.button;
   }
-  return aEvent.type == 'contextmenu' ? 2 : 0;
+  return aEvent.type == "contextmenu" ? 2 : 0;
 }
 
 function sendMouseEvent(aEvent, aTarget, aWindow) {
-  if (!['click', 'contextmenu', 'dblclick', 'mousedown', 'mouseup', 'mouseover',
-        'mouseout'].includes(aEvent.type)) {
-    throw new Error("sendMouseEvent doesn't know about event type '" + aEvent.type + "'");
+  if (
+    ![
+      "click",
+      "contextmenu",
+      "dblclick",
+      "mousedown",
+      "mouseup",
+      "mouseover",
+      "mouseout",
+    ].includes(aEvent.type)
+  ) {
+    throw new Error(
+      "sendMouseEvent doesn't know about event type '" + aEvent.type + "'"
+    );
   }
 
   if (!aWindow) {
@@ -167,31 +181,49 @@ function sendMouseEvent(aEvent, aTarget, aWindow) {
     aTarget = aWindow.document.getElementById(aTarget);
   }
 
-  var event = aWindow.document.createEvent('MouseEvent');
+  var event = aWindow.document.createEvent("MouseEvent");
 
-  var typeArg          = aEvent.type;
-  var canBubbleArg     = true;
-  var cancelableArg    = true;
-  var viewArg          = aWindow;
-  var detailArg        = aEvent.detail        || (aEvent.type == 'click'     ||
-                                                  aEvent.type == 'mousedown' ||
-                                                  aEvent.type == 'mouseup' ? 1 :
-                                                  aEvent.type == 'dblclick'? 2 : 0);
-  var screenXArg       = aEvent.screenX       || 0;
-  var screenYArg       = aEvent.screenY       || 0;
-  var clientXArg       = aEvent.clientX       || 0;
-  var clientYArg       = aEvent.clientY       || 0;
-  var ctrlKeyArg       = aEvent.ctrlKey       || false;
-  var altKeyArg        = aEvent.altKey        || false;
-  var shiftKeyArg      = aEvent.shiftKey      || false;
-  var metaKeyArg       = aEvent.metaKey       || false;
-  var buttonArg        = computeButton(aEvent);
+  var typeArg = aEvent.type;
+  var canBubbleArg = true;
+  var cancelableArg = true;
+  var viewArg = aWindow;
+  var detailArg =
+    aEvent.detail ||
+    (aEvent.type == "click" ||
+    aEvent.type == "mousedown" ||
+    aEvent.type == "mouseup"
+      ? 1
+      : aEvent.type == "dblclick"
+      ? 2
+      : 0);
+  var screenXArg = aEvent.screenX || 0;
+  var screenYArg = aEvent.screenY || 0;
+  var clientXArg = aEvent.clientX || 0;
+  var clientYArg = aEvent.clientY || 0;
+  var ctrlKeyArg = aEvent.ctrlKey || false;
+  var altKeyArg = aEvent.altKey || false;
+  var shiftKeyArg = aEvent.shiftKey || false;
+  var metaKeyArg = aEvent.metaKey || false;
+  var buttonArg = computeButton(aEvent);
   var relatedTargetArg = aEvent.relatedTarget || null;
 
-  event.initMouseEvent(typeArg, canBubbleArg, cancelableArg, viewArg, detailArg,
-                       screenXArg, screenYArg, clientXArg, clientYArg,
-                       ctrlKeyArg, altKeyArg, shiftKeyArg, metaKeyArg,
-                       buttonArg, relatedTargetArg);
+  event.initMouseEvent(
+    typeArg,
+    canBubbleArg,
+    cancelableArg,
+    viewArg,
+    detailArg,
+    screenXArg,
+    screenYArg,
+    clientXArg,
+    clientYArg,
+    ctrlKeyArg,
+    altKeyArg,
+    shiftKeyArg,
+    metaKeyArg,
+    buttonArg,
+    relatedTargetArg
+  );
 
   // If documentURIObject exists or `window` is a stub object, we're in
   // a chrome scope, so don't bother trying to go through SpecialPowers.
@@ -212,8 +244,20 @@ function isHidden(aElement) {
  * have. This includes the type of the drag event.
  */
 function sendDragEvent(aEvent, aTarget, aWindow = window) {
-  if (!['drag', 'dragstart', 'dragend', 'dragover', 'dragenter', 'dragleave', 'drop'].includes(aEvent.type)) {
-    throw new Error("sendDragEvent doesn't know about event type '" + aEvent.type + "'");
+  if (
+    ![
+      "drag",
+      "dragstart",
+      "dragend",
+      "dragover",
+      "dragenter",
+      "dragleave",
+      "drop",
+    ].includes(aEvent.type)
+  ) {
+    throw new Error(
+      "sendDragEvent doesn't know about event type '" + aEvent.type + "'"
+    );
   }
 
   if (typeof aTarget == "string") {
@@ -224,7 +268,7 @@ function sendDragEvent(aEvent, aTarget, aWindow = window) {
    * Drag event cannot be performed if the element is hidden, except 'dragend'
    * event where the element can becomes hidden after start dragging.
    */
-  if (aEvent.type != 'dragend' && isHidden(aTarget)) {
+  if (aEvent.type != "dragend" && isHidden(aTarget)) {
     var targetName = aTarget.nodeName;
     if ("id" in aTarget && aTarget.id) {
       targetName += "#" + aTarget.id;
@@ -232,29 +276,43 @@ function sendDragEvent(aEvent, aTarget, aWindow = window) {
     throw new Error(`${aEvent.type} event target ${targetName} is hidden`);
   }
 
-  var event = aWindow.document.createEvent('DragEvent');
+  var event = aWindow.document.createEvent("DragEvent");
 
-  var typeArg          = aEvent.type;
-  var canBubbleArg     = true;
-  var cancelableArg    = true;
-  var viewArg          = aWindow;
-  var detailArg        = aEvent.detail        || 0;
-  var screenXArg       = aEvent.screenX       || 0;
-  var screenYArg       = aEvent.screenY       || 0;
-  var clientXArg       = aEvent.clientX       || 0;
-  var clientYArg       = aEvent.clientY       || 0;
-  var ctrlKeyArg       = aEvent.ctrlKey       || false;
-  var altKeyArg        = aEvent.altKey        || false;
-  var shiftKeyArg      = aEvent.shiftKey      || false;
-  var metaKeyArg       = aEvent.metaKey       || false;
-  var buttonArg        = computeButton(aEvent);
+  var typeArg = aEvent.type;
+  var canBubbleArg = true;
+  var cancelableArg = true;
+  var viewArg = aWindow;
+  var detailArg = aEvent.detail || 0;
+  var screenXArg = aEvent.screenX || 0;
+  var screenYArg = aEvent.screenY || 0;
+  var clientXArg = aEvent.clientX || 0;
+  var clientYArg = aEvent.clientY || 0;
+  var ctrlKeyArg = aEvent.ctrlKey || false;
+  var altKeyArg = aEvent.altKey || false;
+  var shiftKeyArg = aEvent.shiftKey || false;
+  var metaKeyArg = aEvent.metaKey || false;
+  var buttonArg = computeButton(aEvent);
   var relatedTargetArg = aEvent.relatedTarget || null;
-  var dataTransfer     = aEvent.dataTransfer  || null;
+  var dataTransfer = aEvent.dataTransfer || null;
 
-  event.initDragEvent(typeArg, canBubbleArg, cancelableArg, viewArg, detailArg,
-                      screenXArg, screenYArg, clientXArg, clientYArg,
-                      ctrlKeyArg, altKeyArg, shiftKeyArg, metaKeyArg,
-                      buttonArg, relatedTargetArg, dataTransfer);
+  event.initDragEvent(
+    typeArg,
+    canBubbleArg,
+    cancelableArg,
+    viewArg,
+    detailArg,
+    screenXArg,
+    screenYArg,
+    clientXArg,
+    clientYArg,
+    ctrlKeyArg,
+    altKeyArg,
+    shiftKeyArg,
+    metaKeyArg,
+    buttonArg,
+    relatedTargetArg,
+    dataTransfer
+  );
 
   if (aEvent._domDispatchOnly) {
     return aTarget.dispatchEvent(event);
@@ -291,7 +349,7 @@ function sendChar(aChar, aWindow) {
     case "{":
     case "}":
     case ":":
-    case "\"":
+    case '"':
     case "|":
     case "<":
     case ">":
@@ -299,8 +357,9 @@ function sendChar(aChar, aWindow) {
       hasShift = true;
       break;
     default:
-      hasShift = aChar.toLowerCase() != aChar.toUpperCase() &&
-                 aChar == aChar.toUpperCase();
+      hasShift =
+        aChar.toLowerCase() != aChar.toUpperCase() &&
+        aChar == aChar.toUpperCase();
       break;
   }
   synthesizeKey(aChar, { shiftKey: hasShift }, aWindow);
@@ -333,8 +392,7 @@ function sendKey(aKey, aWindow) {
  * Parse the key modifier flags from aEvent. Used to share code between
  * synthesizeMouse and synthesizeKey.
  */
-function _parseModifiers(aEvent, aWindow = window)
-{
+function _parseModifiers(aEvent, aWindow = window) {
   var navigator = _getNavigator(aWindow);
   var nsIDOMWindowUtils = _EU_Ci.nsIDOMWindowUtils;
   var mval = 0;
@@ -351,8 +409,9 @@ function _parseModifiers(aEvent, aWindow = window)
     mval |= nsIDOMWindowUtils.MODIFIER_META;
   }
   if (aEvent.accelKey) {
-    mval |= _EU_isMac(aWindow) ?
-      nsIDOMWindowUtils.MODIFIER_META : nsIDOMWindowUtils.MODIFIER_CONTROL;
+    mval |= _EU_isMac(aWindow)
+      ? nsIDOMWindowUtils.MODIFIER_META
+      : nsIDOMWindowUtils.MODIFIER_CONTROL;
   }
   if (aEvent.altGrKey) {
     mval |= nsIDOMWindowUtils.MODIFIER_ALTGRAPH;
@@ -400,17 +459,23 @@ function _parseModifiers(aEvent, aWindow = window)
  *
  * Returns whether the event had preventDefault() called on it.
  */
-function synthesizeMouse(aTarget, aOffsetX, aOffsetY, aEvent, aWindow)
-{
+function synthesizeMouse(aTarget, aOffsetX, aOffsetY, aEvent, aWindow) {
   var rect = aTarget.getBoundingClientRect();
-  return synthesizeMouseAtPoint(rect.left + aOffsetX, rect.top + aOffsetY,
-       aEvent, aWindow);
+  return synthesizeMouseAtPoint(
+    rect.left + aOffsetX,
+    rect.top + aOffsetY,
+    aEvent,
+    aWindow
+  );
 }
-function synthesizeTouch(aTarget, aOffsetX, aOffsetY, aEvent, aWindow)
-{
+function synthesizeTouch(aTarget, aOffsetX, aOffsetY, aEvent, aWindow) {
   var rect = aTarget.getBoundingClientRect();
-  return synthesizeTouchAtPoint(rect.left + aOffsetX, rect.top + aOffsetY,
-       aEvent, aWindow);
+  return synthesizeTouchAtPoint(
+    rect.left + aOffsetX,
+    rect.top + aOffsetY,
+    aEvent,
+    aWindow
+  );
 }
 
 /*
@@ -424,8 +489,7 @@ function synthesizeTouch(aTarget, aOffsetX, aOffsetY, aEvent, aWindow)
  *
  * aWindow is optional, and defaults to the current window object.
  */
-function synthesizeMouseAtPoint(left, top, aEvent, aWindow = window)
-{
+function synthesizeMouseAtPoint(left, top, aEvent, aWindow = window) {
   var utils = _getDOMWindowUtils(aWindow);
   var defaultPrevented = false;
 
@@ -433,53 +497,89 @@ function synthesizeMouseAtPoint(left, top, aEvent, aWindow = window)
     var button = computeButton(aEvent);
     var clickCount = aEvent.clickCount || 1;
     var modifiers = _parseModifiers(aEvent, aWindow);
-    var pressure = ("pressure" in aEvent) ? aEvent.pressure : 0;
+    var pressure = "pressure" in aEvent ? aEvent.pressure : 0;
 
     // aWindow might be cross-origin from us.
     var MouseEvent = _EU_maybeWrap(aWindow).MouseEvent;
 
     // Default source to mouse.
-    var inputSource = ("inputSource" in aEvent) ? aEvent.inputSource :
-                                                  MouseEvent.MOZ_SOURCE_MOUSE;
+    var inputSource =
+      "inputSource" in aEvent
+        ? aEvent.inputSource
+        : MouseEvent.MOZ_SOURCE_MOUSE;
     // Compute a pointerId if needed.
     var id;
     if ("id" in aEvent) {
       id = aEvent.id;
     } else {
       var isFromPen = inputSource === MouseEvent.MOZ_SOURCE_PEN;
-      id = isFromPen ? utils.DEFAULT_PEN_POINTER_ID :
-                       utils.DEFAULT_MOUSE_POINTER_ID;
+      id = isFromPen
+        ? utils.DEFAULT_PEN_POINTER_ID
+        : utils.DEFAULT_MOUSE_POINTER_ID;
     }
 
     var isDOMEventSynthesized =
-      ("isSynthesized" in aEvent) ? aEvent.isSynthesized : true;
+      "isSynthesized" in aEvent ? aEvent.isSynthesized : true;
     var isWidgetEventSynthesized =
-      ("isWidgetEventSynthesized" in aEvent) ? aEvent.isWidgetEventSynthesized : false;
-    var buttons = ("buttons" in aEvent) ? aEvent.buttons :
-                                          utils.MOUSE_BUTTONS_NOT_SPECIFIED;
-    if (("type" in aEvent) && aEvent.type) {
-      defaultPrevented = utils.sendMouseEvent(aEvent.type, left, top, button,
-                                              clickCount, modifiers, false,
-                                              pressure, inputSource,
-                                              isDOMEventSynthesized,
-                                              isWidgetEventSynthesized,
-                                              buttons, id);
-    }
-    else {
-      utils.sendMouseEvent("mousedown", left, top, button, clickCount, modifiers,
-                           false, pressure, inputSource, isDOMEventSynthesized,
-                           isWidgetEventSynthesized, buttons, id);
-      utils.sendMouseEvent("mouseup", left, top, button, clickCount, modifiers,
-                           false, pressure, inputSource, isDOMEventSynthesized,
-                           isWidgetEventSynthesized, buttons, id);
+      "isWidgetEventSynthesized" in aEvent
+        ? aEvent.isWidgetEventSynthesized
+        : false;
+    var buttons =
+      "buttons" in aEvent ? aEvent.buttons : utils.MOUSE_BUTTONS_NOT_SPECIFIED;
+    if ("type" in aEvent && aEvent.type) {
+      defaultPrevented = utils.sendMouseEvent(
+        aEvent.type,
+        left,
+        top,
+        button,
+        clickCount,
+        modifiers,
+        false,
+        pressure,
+        inputSource,
+        isDOMEventSynthesized,
+        isWidgetEventSynthesized,
+        buttons,
+        id
+      );
+    } else {
+      utils.sendMouseEvent(
+        "mousedown",
+        left,
+        top,
+        button,
+        clickCount,
+        modifiers,
+        false,
+        pressure,
+        inputSource,
+        isDOMEventSynthesized,
+        isWidgetEventSynthesized,
+        buttons,
+        id
+      );
+      utils.sendMouseEvent(
+        "mouseup",
+        left,
+        top,
+        button,
+        clickCount,
+        modifiers,
+        false,
+        pressure,
+        inputSource,
+        isDOMEventSynthesized,
+        isWidgetEventSynthesized,
+        buttons,
+        id
+      );
     }
   }
 
   return defaultPrevented;
 }
 
-function synthesizeTouchAtPoint(left, top, aEvent, aWindow = window)
-{
+function synthesizeTouchAtPoint(left, top, aEvent, aWindow = window) {
   var utils = _getDOMWindowUtils(aWindow);
   let defaultPrevented = false;
 
@@ -491,29 +591,60 @@ function synthesizeTouchAtPoint(left, top, aEvent, aWindow = window)
     var force = aEvent.force || 1;
     var modifiers = _parseModifiers(aEvent, aWindow);
 
-    if (("type" in aEvent) && aEvent.type) {
-      defaultPrevented = utils.sendTouchEvent(aEvent.type, [id], [left], [top], [rx], [ry], [angle], [force], modifiers);
-    }
-    else {
-      utils.sendTouchEvent("touchstart", [id], [left], [top], [rx], [ry], [angle], [force], modifiers);
-      utils.sendTouchEvent("touchend", [id], [left], [top], [rx], [ry], [angle], [force], modifiers);
+    if ("type" in aEvent && aEvent.type) {
+      defaultPrevented = utils.sendTouchEvent(
+        aEvent.type,
+        [id],
+        [left],
+        [top],
+        [rx],
+        [ry],
+        [angle],
+        [force],
+        modifiers
+      );
+    } else {
+      utils.sendTouchEvent(
+        "touchstart",
+        [id],
+        [left],
+        [top],
+        [rx],
+        [ry],
+        [angle],
+        [force],
+        modifiers
+      );
+      utils.sendTouchEvent(
+        "touchend",
+        [id],
+        [left],
+        [top],
+        [rx],
+        [ry],
+        [angle],
+        [force],
+        modifiers
+      );
     }
   }
   return defaultPrevented;
 }
 
 // Call synthesizeMouse with coordinates at the center of aTarget.
-function synthesizeMouseAtCenter(aTarget, aEvent, aWindow)
-{
+function synthesizeMouseAtCenter(aTarget, aEvent, aWindow) {
   var rect = aTarget.getBoundingClientRect();
-  return synthesizeMouse(aTarget, rect.width / 2, rect.height / 2, aEvent,
-                         aWindow);
+  return synthesizeMouse(
+    aTarget,
+    rect.width / 2,
+    rect.height / 2,
+    aEvent,
+    aWindow
+  );
 }
-function synthesizeTouchAtCenter(aTarget, aEvent, aWindow)
-{
+function synthesizeTouchAtCenter(aTarget, aEvent, aWindow) {
   var rect = aTarget.getBoundingClientRect();
-  synthesizeTouch(aTarget, rect.width / 2, rect.height / 2, aEvent,
-                  aWindow);
+  synthesizeTouch(aTarget, rect.width / 2, rect.height / 2, aEvent, aWindow);
 }
 
 /**
@@ -533,8 +664,7 @@ function synthesizeTouchAtCenter(aTarget, aEvent, aWindow)
  *
  * aWindow is optional, and defaults to the current window object.
  */
-function synthesizeWheelAtPoint(aLeft, aTop, aEvent, aWindow = window)
-{
+function synthesizeWheelAtPoint(aLeft, aTop, aEvent, aWindow = window) {
   var utils = _getDOMWindowUtils(aWindow);
   if (!utils) {
     return;
@@ -583,17 +713,29 @@ function synthesizeWheelAtPoint(aLeft, aTop, aEvent, aWindow = window)
   }
 
   var lineOrPageDeltaX =
-    aEvent.lineOrPageDeltaX != null ? aEvent.lineOrPageDeltaX :
-                  aEvent.deltaX > 0 ? Math.floor(aEvent.deltaX) :
-                                      Math.ceil(aEvent.deltaX);
+    aEvent.lineOrPageDeltaX != null
+      ? aEvent.lineOrPageDeltaX
+      : aEvent.deltaX > 0
+      ? Math.floor(aEvent.deltaX)
+      : Math.ceil(aEvent.deltaX);
   var lineOrPageDeltaY =
-    aEvent.lineOrPageDeltaY != null ? aEvent.lineOrPageDeltaY :
-                  aEvent.deltaY > 0 ? Math.floor(aEvent.deltaY) :
-                                      Math.ceil(aEvent.deltaY);
-  utils.sendWheelEvent(aLeft, aTop,
-                       aEvent.deltaX, aEvent.deltaY, aEvent.deltaZ,
-                       aEvent.deltaMode, modifiers,
-                       lineOrPageDeltaX, lineOrPageDeltaY, options);
+    aEvent.lineOrPageDeltaY != null
+      ? aEvent.lineOrPageDeltaY
+      : aEvent.deltaY > 0
+      ? Math.floor(aEvent.deltaY)
+      : Math.ceil(aEvent.deltaY);
+  utils.sendWheelEvent(
+    aLeft,
+    aTop,
+    aEvent.deltaX,
+    aEvent.deltaY,
+    aEvent.deltaZ,
+    aEvent.deltaMode,
+    modifiers,
+    lineOrPageDeltaX,
+    lineOrPageDeltaY,
+    options
+  );
 }
 
 /**
@@ -614,25 +756,32 @@ function synthesizeWheelAtPoint(aLeft, aTop, aEvent, aWindow = window)
  *
  * aWindow is optional, and defaults to the current window object.
  */
-function synthesizeWheel(aTarget, aOffsetX, aOffsetY, aEvent, aWindow)
-{
+function synthesizeWheel(aTarget, aOffsetX, aOffsetY, aEvent, aWindow) {
   var rect = aTarget.getBoundingClientRect();
-  synthesizeWheelAtPoint(rect.left + aOffsetX, rect.top + aOffsetY,
-                         aEvent, aWindow);
+  synthesizeWheelAtPoint(
+    rect.left + aOffsetX,
+    rect.top + aOffsetY,
+    aEvent,
+    aWindow
+  );
 }
 
 const _FlushModes = {
   FLUSH: 0,
-  NOFLUSH: 1
+  NOFLUSH: 1,
 };
 
-function _sendWheelAndPaint(aTarget, aOffsetX, aOffsetY,
-                            aEvent, aCallback,
-                            aFlushMode = _FlushModes.FLUSH,
-                            aWindow = window) {
+function _sendWheelAndPaint(
+  aTarget,
+  aOffsetX,
+  aOffsetY,
+  aEvent,
+  aCallback,
+  aFlushMode = _FlushModes.FLUSH,
+  aWindow = window
+) {
   var utils = _getDOMWindowUtils(aWindow);
-  if (!utils)
-    return;
+  if (!utils) return;
 
   if (utils.isMozAfterPaintPending) {
     // If a paint is pending, then APZ may be waiting for a scroll acknowledgement
@@ -640,10 +789,15 @@ function _sendWheelAndPaint(aTarget, aOffsetX, aOffsetY,
     // by APZ (or its scroll offset could be overridden). To avoid problems we
     // just wait for the paint to complete.
     aWindow.waitForAllPaintsFlushed(function() {
-      _sendWheelAndPaint(aTarget, aOffsetX, aOffsetY,
-                         aEvent, aCallback,
-                         aFlushMode,
-                         aWindow);
+      _sendWheelAndPaint(
+        aTarget,
+        aOffsetX,
+        aOffsetY,
+        aEvent,
+        aCallback,
+        aFlushMode,
+        aWindow
+      );
     });
     return;
   }
@@ -661,15 +815,21 @@ function _sendWheelAndPaint(aTarget, aOffsetX, aOffsetY,
         return;
       }
 
-      var waitForPaints = function () {
-        SpecialPowers.Services.obs.removeObserver(waitForPaints, "apz-repaints-flushed");
+      var waitForPaints = function() {
+        SpecialPowers.Services.obs.removeObserver(
+          waitForPaints,
+          "apz-repaints-flushed"
+        );
         aWindow.waitForAllPaintsFlushed(function() {
           utils.restoreNormalRefresh();
           aCallback();
         });
-      }
+      };
 
-      SpecialPowers.Services.obs.addObserver(waitForPaints, "apz-repaints-flushed");
+      SpecialPowers.Services.obs.addObserver(
+        waitForPaints,
+        "apz-repaints-flushed"
+      );
       if (!utils.flushApzRepaints(aWindow)) {
         waitForPaints();
       }
@@ -698,13 +858,23 @@ function _sendWheelAndPaint(aTarget, aOffsetX, aOffsetY,
  * determining scroll completion and the refresh driver is not automatically
  * restored.
  */
-function sendWheelAndPaint(aTarget, aOffsetX, aOffsetY,
-                           aEvent, aCallback,
-                           aWindow = window) {
-  _sendWheelAndPaint(aTarget, aOffsetX, aOffsetY,
-                     aEvent, aCallback,
-                     _FlushModes.FLUSH,
-                     aWindow);
+function sendWheelAndPaint(
+  aTarget,
+  aOffsetX,
+  aOffsetY,
+  aEvent,
+  aCallback,
+  aWindow = window
+) {
+  _sendWheelAndPaint(
+    aTarget,
+    aOffsetX,
+    aOffsetY,
+    aEvent,
+    aCallback,
+    _FlushModes.FLUSH,
+    aWindow
+  );
 }
 
 /**
@@ -712,24 +882,52 @@ function sendWheelAndPaint(aTarget, aOffsetX, aOffsetY,
  * |aTarget| position in |aWindow| before sending the wheel event.
  * |aOffsetX| and |aOffsetY| should be offsets against aWindow.
  */
-function sendWheelAndPaintNoFlush(aTarget, aOffsetX, aOffsetY,
-                                  aEvent, aCallback,
-                                  aWindow = window) {
-  _sendWheelAndPaint(aTarget, aOffsetX, aOffsetY,
-                     aEvent, aCallback,
-                     _FlushModes.NOFLUSH,
-                     aWindow);
+function sendWheelAndPaintNoFlush(
+  aTarget,
+  aOffsetX,
+  aOffsetY,
+  aEvent,
+  aCallback,
+  aWindow = window
+) {
+  _sendWheelAndPaint(
+    aTarget,
+    aOffsetX,
+    aOffsetY,
+    aEvent,
+    aCallback,
+    _FlushModes.NOFLUSH,
+    aWindow
+  );
 }
 
-function synthesizeNativeTapAtCenter(aTarget, aLongTap = false, aCallback = null, aWindow = window) {
+function synthesizeNativeTapAtCenter(
+  aTarget,
+  aLongTap = false,
+  aCallback = null,
+  aWindow = window
+) {
   let rect = aTarget.getBoundingClientRect();
-  return synthesizeNativeTap(aTarget, rect.width / 2, rect.height / 2, aLongTap, aCallback, aWindow);
+  return synthesizeNativeTap(
+    aTarget,
+    rect.width / 2,
+    rect.height / 2,
+    aLongTap,
+    aCallback,
+    aWindow
+  );
 }
 
-function synthesizeNativeTap(aTarget, aOffsetX, aOffsetY, aLongTap = false, aCallback = null, aWindow = window) {
+function synthesizeNativeTap(
+  aTarget,
+  aOffsetX,
+  aOffsetY,
+  aLongTap = false,
+  aCallback = null,
+  aWindow = window
+) {
   let utils = _getDOMWindowUtils(aWindow);
-  if (!utils)
-    return;
+  if (!utils) return;
 
   let scale = utils.screenPixelsPerCSSPixel;
   let rect = aTarget.getBoundingClientRect();
@@ -741,15 +939,20 @@ function synthesizeNativeTap(aTarget, aOffsetX, aOffsetY, aLongTap = false, aCal
       if (aCallback && topic == "mouseevent") {
         aCallback(data);
       }
-    }
+    },
   };
   utils.sendNativeTouchTap(x, y, aLongTap, observer);
 }
 
-function synthesizeNativeMouseMove(aTarget, aOffsetX, aOffsetY, aCallback, aWindow = window) {
+function synthesizeNativeMouseMove(
+  aTarget,
+  aOffsetX,
+  aOffsetY,
+  aCallback,
+  aWindow = window
+) {
   var utils = _getDOMWindowUtils(aWindow);
-  if (!utils)
-    return;
+  if (!utils) return;
 
   var rect = aTarget.getBoundingClientRect();
   var x = aOffsetX + window.mozInnerScreenX + rect.left;
@@ -761,7 +964,7 @@ function synthesizeNativeMouseMove(aTarget, aOffsetX, aOffsetY, aCallback, aWind
       if (aCallback && topic == "mouseevent") {
         aCallback(data);
       }
-    }
+    },
   };
   utils.sendNativeMouseMove(x * scale, y * scale, null, observer);
 }
@@ -773,31 +976,43 @@ function synthesizeNativeMouseMove(aTarget, aOffsetX, aOffsetY, aCallback, aWind
  * This API is supposed to be used in those test cases that synthesize some
  * input events to chrome process and have some checks in content.
  */
-function synthesizeAndWaitNativeMouseMove(aTarget, aOffsetX, aOffsetY,
-                                          aCallback, aWindow = window) {
+function synthesizeAndWaitNativeMouseMove(
+  aTarget,
+  aOffsetX,
+  aOffsetY,
+  aCallback,
+  aWindow = window
+) {
   let browser = gBrowser.selectedTab.linkedBrowser;
   let mm = browser.messageManager;
-  let ContentTask =
-    _EU_Cu.import("resource://testing-common/ContentTask.jsm", null).ContentTask;
+  let ContentTask = _EU_Cu.import(
+    "resource://testing-common/ContentTask.jsm",
+    null
+  ).ContentTask;
 
   let eventRegisteredPromise = new Promise(resolve => {
-    mm.addMessageListener("Test:MouseMoveRegistered", function processed(message) {
+    mm.addMessageListener("Test:MouseMoveRegistered", function processed(
+      message
+    ) {
       mm.removeMessageListener("Test:MouseMoveRegistered", processed);
       resolve();
     });
   });
-  let eventReceivedPromise = ContentTask.spawn(browser, [aOffsetX, aOffsetY],
-                                               ([clientX, clientY]) => {
-    return new Promise(resolve => {
-      addEventListener("mousemove", function onMouseMoveEvent(e) {
-        if (e.clientX == clientX && e.clientY == clientY) {
-          removeEventListener("mousemove", onMouseMoveEvent);
-          resolve();
-        }
+  let eventReceivedPromise = ContentTask.spawn(
+    browser,
+    [aOffsetX, aOffsetY],
+    ([clientX, clientY]) => {
+      return new Promise(resolve => {
+        addEventListener("mousemove", function onMouseMoveEvent(e) {
+          if (e.clientX == clientX && e.clientY == clientY) {
+            removeEventListener("mousemove", onMouseMoveEvent);
+            resolve();
+          }
+        });
+        sendAsyncMessage("Test:MouseMoveRegistered");
       });
-      sendAsyncMessage("Test:MouseMoveRegistered");
-    });
-  });
+    }
+  );
   eventRegisteredPromise.then(() => {
     synthesizeNativeMouseMove(aTarget, aOffsetX, aOffsetY, null, aWindow);
   });
@@ -848,8 +1063,7 @@ function synthesizeAndWaitNativeMouseMove(aTarget, aOffsetX, aOffsetY,
  * aWindow is optional, and defaults to the current window object.
  * aCallback is optional, use the callback for receiving notifications of TIP.
  */
-function synthesizeKey(aKey, aEvent = undefined, aWindow = window, aCallback)
-{
+function synthesizeKey(aKey, aEvent = undefined, aWindow = window, aCallback) {
   var event = aEvent === undefined || aEvent === null ? {} : aEvent;
 
   var TIP = _getTIP(aWindow, aCallback);
@@ -863,7 +1077,7 @@ function synthesizeKey(aKey, aEvent = undefined, aWindow = window, aCallback)
   var dispatchKeydown =
     !("type" in event) || event.type === "keydown" || !event.type;
   var dispatchKeyup =
-    !("type" in event) || event.type === "keyup"   || !event.type;
+    !("type" in event) || event.type === "keyup" || !event.type;
 
   try {
     if (dispatchKeydown) {
@@ -892,13 +1106,21 @@ function synthesizeKey(aKey, aEvent = undefined, aWindow = window, aCallback)
  * This API is supposed to be used in those test cases that synthesize some
  * input events to chrome process and have some checks in content.
  */
-function synthesizeAndWaitKey(aKey, aEvent, aWindow = window,
-                              checkBeforeSynthesize, checkAfterSynthesize)
-{
+function synthesizeAndWaitKey(
+  aKey,
+  aEvent,
+  aWindow = window,
+  checkBeforeSynthesize,
+  checkAfterSynthesize
+) {
   let browser = gBrowser.selectedTab.linkedBrowser;
   let mm = browser.messageManager;
-  let keyCode = _createKeyboardEventDictionary(aKey, aEvent, null, aWindow).dictionary.keyCode;
-  let ContentTask = _EU_Cu.import("resource://testing-common/ContentTask.jsm", null).ContentTask;
+  let keyCode = _createKeyboardEventDictionary(aKey, aEvent, null, aWindow)
+    .dictionary.keyCode;
+  let ContentTask = _EU_Cu.import(
+    "resource://testing-common/ContentTask.jsm",
+    null
+  ).ContentTask;
 
   let keyRegisteredPromise = new Promise(resolve => {
     mm.addMessageListener("Test:KeyRegistered", function processed(message) {
@@ -906,7 +1128,7 @@ function synthesizeAndWaitKey(aKey, aEvent, aWindow = window,
       resolve();
     });
   });
-  let keyReceivedPromise = ContentTask.spawn(browser, keyCode, (keyCode) => {
+  let keyReceivedPromise = ContentTask.spawn(browser, keyCode, keyCode => {
     return new Promise(resolve => {
       addEventListener("keyup", function onKeyEvent(e) {
         if (e.keyCode == keyCode) {
@@ -929,8 +1151,7 @@ function synthesizeAndWaitKey(aKey, aEvent, aWindow = window,
   return keyReceivedPromise;
 }
 
-function _parseNativeModifiers(aModifiers, aWindow = window)
-{
+function _parseNativeModifiers(aModifiers, aWindow = window) {
   var navigator = _getNavigator(aWindow);
   var modifiers;
   if (aModifiers.capsLockKey) {
@@ -991,57 +1212,108 @@ function _parseNativeModifiers(aModifiers, aWindow = window)
 // Win: These constants can be found by inspecting registry keys under
 //      HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Keyboard Layouts
 
-const KEYBOARD_LAYOUT_ARABIC =
-  { name: "Arabic",             Mac: 6,
-                                Win: 0x00000401, hasAltGrOnWin: false };
-const KEYBOARD_LAYOUT_ARABIC_PC =
-  { name: "Arabic - PC",        Mac: 7,
-                                Win: null,       hasAltGrOnWin: false };
-const KEYBOARD_LAYOUT_BRAZILIAN_ABNT =
-  { name: "Brazilian ABNT",     Mac: null,
-                                Win: 0x00000416, hasAltGrOnWin: true  };
-const KEYBOARD_LAYOUT_DVORAK_QWERTY =
-  { name: "Dvorak-QWERTY",      Mac: 4,
-                                Win: null,       hasAltGrOnWin: false };
-const KEYBOARD_LAYOUT_EN_US =
-  { name: "US",                 Mac: 0,
-                                Win: 0x00000409, hasAltGrOnWin: false };
-const KEYBOARD_LAYOUT_FRENCH =
-  { name: "French",             Mac: 8,
-                                Win: 0x0000040C, hasAltGrOnWin: true  };
-const KEYBOARD_LAYOUT_GREEK =
-  { name: "Greek",              Mac: 1,
-                                Win: 0x00000408, hasAltGrOnWin: true  };
-const KEYBOARD_LAYOUT_GERMAN =
-  { name: "German",             Mac: 2,
-                                Win: 0x00000407, hasAltGrOnWin: true  };
-const KEYBOARD_LAYOUT_HEBREW =
-  { name: "Hebrew",             Mac: 9,
-                                Win: 0x0000040D, hasAltGrOnWin: true  };
-const KEYBOARD_LAYOUT_JAPANESE =
-  { name: "Japanese",           Mac: null,
-                                Win: 0x00000411, hasAltGrOnWin: false };
-const KEYBOARD_LAYOUT_KHMER =
-  { name: "Khmer",              Mac: null,
-                                Win: 0x00000453, hasAltGrOnWin: true  }; // available on Win7 or later.
-const KEYBOARD_LAYOUT_LITHUANIAN =
-  { name: "Lithuanian",         Mac: 10,
-                                Win: 0x00010427, hasAltGrOnWin: true  };
-const KEYBOARD_LAYOUT_NORWEGIAN =
-  { name: "Norwegian",          Mac: 11,
-                                Win: 0x00000414, hasAltGrOnWin: true  };
-const KEYBOARD_LAYOUT_RUSSIAN_MNEMONIC =
-  { name: "Russian - Mnemonic", Mac: null,
-                                Win: 0x00020419, hasAltGrOnWin: true  }; // available on Win8 or later.
-const KEYBOARD_LAYOUT_SPANISH =
-  { name: "Spanish",            Mac: 12,
-                                Win: 0x0000040A, hasAltGrOnWin: true  };
-const KEYBOARD_LAYOUT_SWEDISH =
-  { name: "Swedish",            Mac: 3,
-                                Win: 0x0000041D, hasAltGrOnWin: true  };
-const KEYBOARD_LAYOUT_THAI =
-  { name: "Thai",               Mac: 5,
-                                Win: 0x0002041E, hasAltGrOnWin: false };
+const KEYBOARD_LAYOUT_ARABIC = {
+  name: "Arabic",
+  Mac: 6,
+  Win: 0x00000401,
+  hasAltGrOnWin: false,
+};
+const KEYBOARD_LAYOUT_ARABIC_PC = {
+  name: "Arabic - PC",
+  Mac: 7,
+  Win: null,
+  hasAltGrOnWin: false,
+};
+const KEYBOARD_LAYOUT_BRAZILIAN_ABNT = {
+  name: "Brazilian ABNT",
+  Mac: null,
+  Win: 0x00000416,
+  hasAltGrOnWin: true,
+};
+const KEYBOARD_LAYOUT_DVORAK_QWERTY = {
+  name: "Dvorak-QWERTY",
+  Mac: 4,
+  Win: null,
+  hasAltGrOnWin: false,
+};
+const KEYBOARD_LAYOUT_EN_US = {
+  name: "US",
+  Mac: 0,
+  Win: 0x00000409,
+  hasAltGrOnWin: false,
+};
+const KEYBOARD_LAYOUT_FRENCH = {
+  name: "French",
+  Mac: 8,
+  Win: 0x0000040c,
+  hasAltGrOnWin: true,
+};
+const KEYBOARD_LAYOUT_GREEK = {
+  name: "Greek",
+  Mac: 1,
+  Win: 0x00000408,
+  hasAltGrOnWin: true,
+};
+const KEYBOARD_LAYOUT_GERMAN = {
+  name: "German",
+  Mac: 2,
+  Win: 0x00000407,
+  hasAltGrOnWin: true,
+};
+const KEYBOARD_LAYOUT_HEBREW = {
+  name: "Hebrew",
+  Mac: 9,
+  Win: 0x0000040d,
+  hasAltGrOnWin: true,
+};
+const KEYBOARD_LAYOUT_JAPANESE = {
+  name: "Japanese",
+  Mac: null,
+  Win: 0x00000411,
+  hasAltGrOnWin: false,
+};
+const KEYBOARD_LAYOUT_KHMER = {
+  name: "Khmer",
+  Mac: null,
+  Win: 0x00000453,
+  hasAltGrOnWin: true,
+}; // available on Win7 or later.
+const KEYBOARD_LAYOUT_LITHUANIAN = {
+  name: "Lithuanian",
+  Mac: 10,
+  Win: 0x00010427,
+  hasAltGrOnWin: true,
+};
+const KEYBOARD_LAYOUT_NORWEGIAN = {
+  name: "Norwegian",
+  Mac: 11,
+  Win: 0x00000414,
+  hasAltGrOnWin: true,
+};
+const KEYBOARD_LAYOUT_RUSSIAN_MNEMONIC = {
+  name: "Russian - Mnemonic",
+  Mac: null,
+  Win: 0x00020419,
+  hasAltGrOnWin: true,
+}; // available on Win8 or later.
+const KEYBOARD_LAYOUT_SPANISH = {
+  name: "Spanish",
+  Mac: 12,
+  Win: 0x0000040a,
+  hasAltGrOnWin: true,
+};
+const KEYBOARD_LAYOUT_SWEDISH = {
+  name: "Swedish",
+  Mac: 3,
+  Win: 0x0000041d,
+  hasAltGrOnWin: true,
+};
+const KEYBOARD_LAYOUT_THAI = {
+  name: "Thai",
+  Mac: 5,
+  Win: 0x0002041e,
+  hasAltGrOnWin: false,
+};
 
 /**
  * synthesizeNativeKey() dispatches native key event on active window.
@@ -1069,9 +1341,15 @@ const KEYBOARD_LAYOUT_THAI =
  *                              native key event.  Otherwise, false.
  */
 
-function synthesizeNativeKey(aKeyboardLayout, aNativeKeyCode, aModifiers,
-                             aChars, aUnmodifiedChars, aCallback, aWindow = window)
-{
+function synthesizeNativeKey(
+  aKeyboardLayout,
+  aNativeKeyCode,
+  aModifiers,
+  aChars,
+  aUnmodifiedChars,
+  aCallback,
+  aWindow = window
+) {
   var utils = _getDOMWindowUtils(aWindow);
   if (!utils) {
     return false;
@@ -1092,11 +1370,16 @@ function synthesizeNativeKey(aKeyboardLayout, aNativeKeyCode, aModifiers,
       if (aCallback && aTopic == "keyevent") {
         aCallback(aData);
       }
-    }
+    },
   };
-  utils.sendNativeKeyEvent(nativeKeyboardLayout, aNativeKeyCode,
-                           _parseNativeModifiers(aModifiers, aWindow),
-                           aChars, aUnmodifiedChars, observer);
+  utils.sendNativeKeyEvent(
+    nativeKeyboardLayout,
+    aNativeKeyCode,
+    _parseNativeModifiers(aModifiers, aWindow),
+    aChars,
+    aUnmodifiedChars,
+    observer
+  );
   return true;
 }
 
@@ -1107,19 +1390,25 @@ var _gSeenEvent = false;
  * a type of aExpectedEvent is expected to be fired, or not expected to
  * be fired.
  */
-function _expectEvent(aExpectedTarget, aExpectedEvent, aTestName)
-{
-  if (!aExpectedTarget || !aExpectedEvent)
-    return null;
+function _expectEvent(aExpectedTarget, aExpectedEvent, aTestName) {
+  if (!aExpectedTarget || !aExpectedEvent) return null;
 
   _gSeenEvent = false;
 
-  var type = (aExpectedEvent.charAt(0) == "!") ?
-             aExpectedEvent.substring(1) : aExpectedEvent;
+  var type =
+    aExpectedEvent.charAt(0) == "!"
+      ? aExpectedEvent.substring(1)
+      : aExpectedEvent;
   var eventHandler = function(event) {
-    var epassed = (!_gSeenEvent && event.originalTarget == aExpectedTarget &&
-                   event.type == type);
-    is(epassed, true, aTestName + " " + type + " event target " + (_gSeenEvent ? "twice" : ""));
+    var epassed =
+      !_gSeenEvent &&
+      event.originalTarget == aExpectedTarget &&
+      event.type == type;
+    is(
+      epassed,
+      true,
+      aTestName + " " + type + " event target " + (_gSeenEvent ? "twice" : "")
+    );
     _gSeenEvent = true;
   };
 
@@ -1131,15 +1420,18 @@ function _expectEvent(aExpectedTarget, aExpectedEvent, aTestName)
  * Check if the event was fired or not. The event handler aEventHandler
  * will be removed.
  */
-function _checkExpectedEvent(aExpectedTarget, aExpectedEvent, aEventHandler, aTestName)
-{
+function _checkExpectedEvent(
+  aExpectedTarget,
+  aExpectedEvent,
+  aEventHandler,
+  aTestName
+) {
   if (aEventHandler) {
-    var expectEvent = (aExpectedEvent.charAt(0) != "!");
+    var expectEvent = aExpectedEvent.charAt(0) != "!";
     var type = expectEvent ? aExpectedEvent : aExpectedEvent.substring(1);
     aExpectedTarget.removeEventListener(type, aEventHandler);
     var desc = type + " event";
-    if (!expectEvent)
-      desc += " not";
+    if (!expectEvent) desc += " not";
     is(_gSeenEvent, expectEvent, aTestName + " " + desc + " fired");
   }
 
@@ -1160,10 +1452,16 @@ function _checkExpectedEvent(aExpectedTarget, aExpectedEvent, aEventHandler, aTe
  *
  * aWindow is optional, and defaults to the current window object.
  */
-function synthesizeMouseExpectEvent(aTarget, aOffsetX, aOffsetY, aEvent,
-                                    aExpectedTarget, aExpectedEvent, aTestName,
-                                    aWindow)
-{
+function synthesizeMouseExpectEvent(
+  aTarget,
+  aOffsetX,
+  aOffsetY,
+  aEvent,
+  aExpectedTarget,
+  aExpectedEvent,
+  aTestName,
+  aWindow
+) {
   var eventHandler = _expectEvent(aExpectedTarget, aExpectedEvent, aTestName);
   synthesizeMouse(aTarget, aOffsetX, aOffsetY, aEvent, aWindow);
   _checkExpectedEvent(aExpectedTarget, aExpectedEvent, eventHandler, aTestName);
@@ -1182,22 +1480,25 @@ function synthesizeMouseExpectEvent(aTarget, aOffsetX, aOffsetY, aEvent,
  *
  * aWindow is optional, and defaults to the current window object.
  */
-function synthesizeKeyExpectEvent(key, aEvent, aExpectedTarget, aExpectedEvent,
-                                  aTestName, aWindow)
-{
+function synthesizeKeyExpectEvent(
+  key,
+  aEvent,
+  aExpectedTarget,
+  aExpectedEvent,
+  aTestName,
+  aWindow
+) {
   var eventHandler = _expectEvent(aExpectedTarget, aExpectedEvent, aTestName);
   synthesizeKey(key, aEvent, aWindow);
   _checkExpectedEvent(aExpectedTarget, aExpectedEvent, eventHandler, aTestName);
 }
 
-function disableNonTestMouseEvents(aDisable)
-{
+function disableNonTestMouseEvents(aDisable) {
   var domutils = _getDOMWindowUtils();
   domutils.disableNonTestMouseEvents(aDisable);
 }
 
-function _getDOMWindowUtils(aWindow = window)
-{
+function _getDOMWindowUtils(aWindow = window) {
   // Leave this here as something, somewhere, passes a falsy argument
   // to this, causing the |window| default argument not to get picked up.
   if (!aWindow) {
@@ -1229,7 +1530,7 @@ function _defineConstant(name, value) {
   Object.defineProperty(this, name, {
     value: value,
     enumerable: true,
-    writable: false
+    writable: false,
   });
 }
 
@@ -1238,18 +1539,26 @@ const COMPOSITION_ATTR_RAW_CLAUSE =
 _defineConstant("COMPOSITION_ATTR_RAW_CLAUSE", COMPOSITION_ATTR_RAW_CLAUSE);
 const COMPOSITION_ATTR_SELECTED_RAW_CLAUSE =
   _EU_Ci.nsITextInputProcessor.ATTR_SELECTED_RAW_CLAUSE;
-_defineConstant("COMPOSITION_ATTR_SELECTED_RAW_CLAUSE", COMPOSITION_ATTR_SELECTED_RAW_CLAUSE);
+_defineConstant(
+  "COMPOSITION_ATTR_SELECTED_RAW_CLAUSE",
+  COMPOSITION_ATTR_SELECTED_RAW_CLAUSE
+);
 const COMPOSITION_ATTR_CONVERTED_CLAUSE =
   _EU_Ci.nsITextInputProcessor.ATTR_CONVERTED_CLAUSE;
-_defineConstant("COMPOSITION_ATTR_CONVERTED_CLAUSE", COMPOSITION_ATTR_CONVERTED_CLAUSE);
+_defineConstant(
+  "COMPOSITION_ATTR_CONVERTED_CLAUSE",
+  COMPOSITION_ATTR_CONVERTED_CLAUSE
+);
 const COMPOSITION_ATTR_SELECTED_CLAUSE =
   _EU_Ci.nsITextInputProcessor.ATTR_SELECTED_CLAUSE;
-_defineConstant("COMPOSITION_ATTR_SELECTED_CLAUSE", COMPOSITION_ATTR_SELECTED_CLAUSE);
+_defineConstant(
+  "COMPOSITION_ATTR_SELECTED_CLAUSE",
+  COMPOSITION_ATTR_SELECTED_CLAUSE
+);
 
 var TIPMap = new WeakMap();
 
-function _getTIP(aWindow, aCallback)
-{
+function _getTIP(aWindow, aCallback) {
   if (!aWindow) {
     aWindow = window;
   }
@@ -1257,9 +1566,9 @@ function _getTIP(aWindow, aCallback)
   if (TIPMap.has(aWindow)) {
     tip = TIPMap.get(aWindow);
   } else {
-    tip =
-      _EU_Cc["@mozilla.org/text-input-processor;1"].
-        createInstance(_EU_Ci.nsITextInputProcessor);
+    tip = _EU_Cc["@mozilla.org/text-input-processor;1"].createInstance(
+      _EU_Ci.nsITextInputProcessor
+    );
     TIPMap.set(aWindow, tip);
   }
   if (!tip.beginInputTransactionForTests(aWindow, aCallback)) {
@@ -1269,8 +1578,7 @@ function _getTIP(aWindow, aCallback)
   return tip;
 }
 
-function _getKeyboardEvent(aWindow = window)
-{
+function _getKeyboardEvent(aWindow = window) {
   if (typeof KeyboardEvent != "undefined") {
     try {
       // See if the object can be instantiated; sometimes this yields
@@ -1279,22 +1587,20 @@ function _getKeyboardEvent(aWindow = window)
       return KeyboardEvent;
     } catch (ex) {}
   }
-  if (typeof content != "undefined" && ("KeyboardEvent" in content)) {
+  if (typeof content != "undefined" && "KeyboardEvent" in content) {
     return content.KeyboardEvent;
   }
   return aWindow.KeyboardEvent;
 }
 
-function _getNavigator(aWindow = window)
-{
+function _getNavigator(aWindow = window) {
   if (typeof navigator != "undefined") {
     return navigator;
   }
   return aWindow.navigator;
 }
 
-function _guessKeyNameFromKeyCode(aKeyCode, aWindow = window)
-{
+function _guessKeyNameFromKeyCode(aKeyCode, aWindow = window) {
   var KeyboardEvent = _getKeyboardEvent(aWindow);
   switch (aKeyCode) {
     case KeyboardEvent.DOM_VK_CANCEL:
@@ -1442,14 +1748,18 @@ function _guessKeyNameFromKeyCode(aKeyCode, aWindow = window)
   }
 }
 
-function _createKeyboardEventDictionary(aKey, aKeyEvent,
-                                        aTIP = null,
-                                        aWindow = window) {
+function _createKeyboardEventDictionary(
+  aKey,
+  aKeyEvent,
+  aTIP = null,
+  aWindow = window
+) {
   var result = { dictionary: null, flags: 0 };
   var keyCodeIsDefined = "keyCode" in aKeyEvent;
   var keyCode =
-    (keyCodeIsDefined && aKeyEvent.keyCode >= 0 && aKeyEvent.keyCode <= 255) ?
-      aKeyEvent.keyCode : 0;
+    keyCodeIsDefined && aKeyEvent.keyCode >= 0 && aKeyEvent.keyCode <= 255
+      ? aKeyEvent.keyCode
+      : 0;
   var keyName = "Unidentified";
   var code = aKeyEvent.code;
   if (!aTIP) {
@@ -1459,8 +1769,10 @@ function _createKeyboardEventDictionary(aKey, aKeyEvent,
     keyName = aKey.substr("KEY_".length);
     result.flags |= _EU_Ci.nsITextInputProcessor.KEY_NON_PRINTABLE_KEY;
     if (code === undefined) {
-      code =
-        aTIP.computeCodeValueOfNonPrintableKey(keyName, aKeyEvent.location);
+      code = aTIP.computeCodeValueOfNonPrintableKey(
+        keyName,
+        aKeyEvent.location
+      );
     }
   } else if (aKey.indexOf("VK_") == 0) {
     keyCode = _getKeyboardEvent(aWindow)["DOM_" + aKey];
@@ -1470,15 +1782,18 @@ function _createKeyboardEventDictionary(aKey, aKeyEvent,
     keyName = _guessKeyNameFromKeyCode(keyCode, aWindow);
     result.flags |= _EU_Ci.nsITextInputProcessor.KEY_NON_PRINTABLE_KEY;
     if (code === undefined) {
-      code =
-        aTIP.computeCodeValueOfNonPrintableKey(keyName, aKeyEvent.location);
+      code = aTIP.computeCodeValueOfNonPrintableKey(
+        keyName,
+        aKeyEvent.location
+      );
     }
   } else if (aKey != "") {
     keyName = aKey;
     if (!keyCodeIsDefined) {
-      keyCode =
-        aTIP.guessKeyCodeValueOfPrintableKeyInUSEnglishKeyboardLayout(
-               aKey, aKeyEvent.location);
+      keyCode = aTIP.guessKeyCodeValueOfPrintableKeyInUSEnglishKeyboardLayout(
+        aKey,
+        aKeyEvent.location
+      );
     }
     if (!keyCode) {
       result.flags |= _EU_Ci.nsITextInputProcessor.KEY_KEEP_KEYCODE_ZERO;
@@ -1486,7 +1801,9 @@ function _createKeyboardEventDictionary(aKey, aKeyEvent,
     result.flags |= _EU_Ci.nsITextInputProcessor.KEY_FORCE_PRINTABLE_KEY;
     if (code === undefined) {
       code = aTIP.guessCodeValueOfPrintableKeyInUSEnglishKeyboardLayout(
-               keyName, aKeyEvent.location);
+        keyName,
+        aKeyEvent.location
+      );
     }
   }
   var locationIsDefined = "location" in aKeyEvent;
@@ -1510,8 +1827,7 @@ function _createKeyboardEventDictionary(aKey, aKeyEvent,
   return result;
 }
 
-function _emulateToActivateModifiers(aTIP, aKeyEvent, aWindow = window)
-{
+function _emulateToActivateModifiers(aTIP, aKeyEvent, aWindow = window) {
   if (!aKeyEvent) {
     return null;
   }
@@ -1520,25 +1836,24 @@ function _emulateToActivateModifiers(aTIP, aKeyEvent, aWindow = window)
 
   var modifiers = {
     normal: [
-      { key: "Alt",        attr: "altKey" },
-      { key: "AltGraph",   attr: "altGraphKey" },
-      { key: "Control",    attr: "ctrlKey" },
-      { key: "Fn",         attr: "fnKey" },
-      { key: "Meta",       attr: "metaKey" },
-      { key: "OS",         attr: "osKey" },
-      { key: "Shift",      attr: "shiftKey" },
-      { key: "Symbol",     attr: "symbolKey" },
-      { key: _EU_isMac(aWindow) ? "Meta" : "Control",
-                           attr: "accelKey" },
+      { key: "Alt", attr: "altKey" },
+      { key: "AltGraph", attr: "altGraphKey" },
+      { key: "Control", attr: "ctrlKey" },
+      { key: "Fn", attr: "fnKey" },
+      { key: "Meta", attr: "metaKey" },
+      { key: "OS", attr: "osKey" },
+      { key: "Shift", attr: "shiftKey" },
+      { key: "Symbol", attr: "symbolKey" },
+      { key: _EU_isMac(aWindow) ? "Meta" : "Control", attr: "accelKey" },
     ],
     lockable: [
-      { key: "CapsLock",   attr: "capsLockKey" },
-      { key: "FnLock",     attr: "fnLockKey" },
-      { key: "NumLock",    attr: "numLockKey" },
+      { key: "CapsLock", attr: "capsLockKey" },
+      { key: "FnLock", attr: "fnLockKey" },
+      { key: "NumLock", attr: "numLockKey" },
       { key: "ScrollLock", attr: "scrollLockKey" },
       { key: "SymbolLock", attr: "symbolLockKey" },
-    ]
-  }
+    ],
+  };
 
   for (var i = 0; i < modifiers.normal.length; i++) {
     if (!aKeyEvent[modifiers.normal[i].attr]) {
@@ -1548,8 +1863,10 @@ function _emulateToActivateModifiers(aTIP, aKeyEvent, aWindow = window)
       continue; // already activated.
     }
     var event = new KeyboardEvent("", { key: modifiers.normal[i].key });
-    aTIP.keydown(event,
-      aTIP.KEY_NON_PRINTABLE_KEY | aTIP.KEY_DONT_DISPATCH_MODIFIER_KEY_EVENT);
+    aTIP.keydown(
+      event,
+      aTIP.KEY_NON_PRINTABLE_KEY | aTIP.KEY_DONT_DISPATCH_MODIFIER_KEY_EVENT
+    );
     modifiers.normal[i].activated = true;
   }
   for (var i = 0; i < modifiers.lockable.length; i++) {
@@ -1560,17 +1877,20 @@ function _emulateToActivateModifiers(aTIP, aKeyEvent, aWindow = window)
       continue; // already activated.
     }
     var event = new KeyboardEvent("", { key: modifiers.lockable[i].key });
-    aTIP.keydown(event,
-      aTIP.KEY_NON_PRINTABLE_KEY | aTIP.KEY_DONT_DISPATCH_MODIFIER_KEY_EVENT);
-    aTIP.keyup(event,
-      aTIP.KEY_NON_PRINTABLE_KEY | aTIP.KEY_DONT_DISPATCH_MODIFIER_KEY_EVENT);
+    aTIP.keydown(
+      event,
+      aTIP.KEY_NON_PRINTABLE_KEY | aTIP.KEY_DONT_DISPATCH_MODIFIER_KEY_EVENT
+    );
+    aTIP.keyup(
+      event,
+      aTIP.KEY_NON_PRINTABLE_KEY | aTIP.KEY_DONT_DISPATCH_MODIFIER_KEY_EVENT
+    );
     modifiers.lockable[i].activated = true;
   }
   return modifiers;
 }
 
-function _emulateToInactivateModifiers(aTIP, aModifiers, aWindow = window)
-{
+function _emulateToInactivateModifiers(aTIP, aModifiers, aWindow = window) {
   if (!aModifiers) {
     return;
   }
@@ -1580,8 +1900,10 @@ function _emulateToInactivateModifiers(aTIP, aModifiers, aWindow = window)
       continue;
     }
     var event = new KeyboardEvent("", { key: aModifiers.normal[i].key });
-    aTIP.keyup(event,
-      aTIP.KEY_NON_PRINTABLE_KEY | aTIP.KEY_DONT_DISPATCH_MODIFIER_KEY_EVENT);
+    aTIP.keyup(
+      event,
+      aTIP.KEY_NON_PRINTABLE_KEY | aTIP.KEY_DONT_DISPATCH_MODIFIER_KEY_EVENT
+    );
   }
   for (var i = 0; i < aModifiers.lockable.length; i++) {
     if (!aModifiers.lockable[i].activated) {
@@ -1591,10 +1913,14 @@ function _emulateToInactivateModifiers(aTIP, aModifiers, aWindow = window)
       continue; // who already inactivated this?
     }
     var event = new KeyboardEvent("", { key: aModifiers.lockable[i].key });
-    aTIP.keydown(event,
-      aTIP.KEY_NON_PRINTABLE_KEY | aTIP.KEY_DONT_DISPATCH_MODIFIER_KEY_EVENT);
-    aTIP.keyup(event,
-      aTIP.KEY_NON_PRINTABLE_KEY | aTIP.KEY_DONT_DISPATCH_MODIFIER_KEY_EVENT);
+    aTIP.keydown(
+      event,
+      aTIP.KEY_NON_PRINTABLE_KEY | aTIP.KEY_DONT_DISPATCH_MODIFIER_KEY_EVENT
+    );
+    aTIP.keyup(
+      event,
+      aTIP.KEY_NON_PRINTABLE_KEY | aTIP.KEY_DONT_DISPATCH_MODIFIER_KEY_EVENT
+    );
   }
 }
 
@@ -1644,8 +1970,7 @@ function _emulateToInactivateModifiers(aTIP, aModifiers, aWindow = window)
  * @param aCallback            Optional (If non-null, use the callback for
  *                             receiving notifications to IME)
  */
-function synthesizeComposition(aEvent, aWindow = window, aCallback)
-{
+function synthesizeComposition(aEvent, aWindow = window, aCallback) {
   var TIP = _getTIP(aWindow, aCallback);
   if (!TIP) {
     return false;
@@ -1653,20 +1978,31 @@ function synthesizeComposition(aEvent, aWindow = window, aCallback)
   var KeyboardEvent = _getKeyboardEvent(aWindow);
   var modifiers = _emulateToActivateModifiers(TIP, aEvent.key, aWindow);
   var ret = false;
-  var keyEventDict = {dictionary: null, flags: 0};
+  var keyEventDict = { dictionary: null, flags: 0 };
   var keyEvent = null;
   if (aEvent.key && typeof aEvent.key.key === "string") {
-    keyEventDict =
-      _createKeyboardEventDictionary(aEvent.key.key, aEvent.key, TIP, aWindow);
-    keyEvent = new KeyboardEvent(aEvent.key.type === "keydown" ?
-                                   "keydown" :
-                                   aEvent.key.type === "keyup" ?
-                                     "keyup" : "",
-                                 keyEventDict.dictionary)
+    keyEventDict = _createKeyboardEventDictionary(
+      aEvent.key.key,
+      aEvent.key,
+      TIP,
+      aWindow
+    );
+    keyEvent = new KeyboardEvent(
+      aEvent.key.type === "keydown"
+        ? "keydown"
+        : aEvent.key.type === "keyup"
+        ? "keyup"
+        : "",
+      keyEventDict.dictionary
+    );
   } else if (aEvent.key === undefined) {
-    keyEventDict =
-      _createKeyboardEventDictionary("KEY_Process", {}, TIP, aWindow);
-    keyEvent = new KeyboardEvent("", keyEventDict.dictionary)
+    keyEventDict = _createKeyboardEventDictionary(
+      "KEY_Process",
+      {},
+      TIP,
+      aWindow
+    );
+    keyEvent = new KeyboardEvent("", keyEventDict.dictionary);
   }
   try {
     switch (aEvent.type) {
@@ -1677,8 +2013,11 @@ function synthesizeComposition(aEvent, aWindow = window, aCallback)
         ret = TIP.commitComposition(keyEvent, keyEventDict.flags);
         break;
       case "compositioncommit":
-        ret = TIP.commitCompositionWith(aEvent.data, keyEvent,
-                                        keyEventDict.flags);
+        ret = TIP.commitCompositionWith(
+          aEvent.data,
+          keyEvent,
+          keyEventDict.flags
+        );
         break;
     }
   } finally {
@@ -1749,16 +2088,18 @@ function synthesizeComposition(aEvent, aWindow = window, aCallback)
  * @param aCallback     Optional (If non-null, use the callback for receiving
  *                      notifications to IME)
  */
-function synthesizeCompositionChange(aEvent, aWindow = window, aCallback)
-{
+function synthesizeCompositionChange(aEvent, aWindow = window, aCallback) {
   var TIP = _getTIP(aWindow, aCallback);
   if (!TIP) {
     return;
   }
   var KeyboardEvent = _getKeyboardEvent(aWindow);
 
-  if (!aEvent.composition || !aEvent.composition.clauses ||
-      !aEvent.composition.clauses[0]) {
+  if (
+    !aEvent.composition ||
+    !aEvent.composition.clauses ||
+    !aEvent.composition.clauses[0]
+  ) {
     return;
   }
 
@@ -1771,8 +2112,9 @@ function synthesizeCompositionChange(aEvent, aWindow = window, aCallback)
         case TIP.ATTR_CONVERTED_CLAUSE:
         case TIP.ATTR_SELECTED_CLAUSE:
           TIP.appendClauseToPendingComposition(
-                aEvent.composition.clauses[i].length,
-                aEvent.composition.clauses[i].attr);
+            aEvent.composition.clauses[i].length,
+            aEvent.composition.clauses[i].attr
+          );
           break;
         case 0:
           // Ignore dummy clause for the argument.
@@ -1790,21 +2132,31 @@ function synthesizeCompositionChange(aEvent, aWindow = window, aCallback)
 
   var modifiers = _emulateToActivateModifiers(TIP, aEvent.key, aWindow);
   try {
-    var keyEventDict = {dictionary: null, flags: 0};
+    var keyEventDict = { dictionary: null, flags: 0 };
     var keyEvent = null;
     if (aEvent.key && typeof aEvent.key.key === "string") {
-      keyEventDict =
-        _createKeyboardEventDictionary(aEvent.key.key, aEvent.key,
-                                       TIP, aWindow);
-      keyEvent = new KeyboardEvent(aEvent.key.type === "keydown" ?
-                                     "keydown" :
-                                     aEvent.key.type === "keyup" ?
-                                       "keyup" : "",
-                                   keyEventDict.dictionary)
+      keyEventDict = _createKeyboardEventDictionary(
+        aEvent.key.key,
+        aEvent.key,
+        TIP,
+        aWindow
+      );
+      keyEvent = new KeyboardEvent(
+        aEvent.key.type === "keydown"
+          ? "keydown"
+          : aEvent.key.type === "keyup"
+          ? "keyup"
+          : "",
+        keyEventDict.dictionary
+      );
     } else if (aEvent.key === undefined) {
-      keyEventDict =
-        _createKeyboardEventDictionary("KEY_Process", {}, TIP, aWindow);
-      keyEvent = new KeyboardEvent("", keyEventDict.dictionary)
+      keyEventDict = _createKeyboardEventDictionary(
+        "KEY_Process",
+        {},
+        TIP,
+        aWindow
+      );
+      keyEvent = new KeyboardEvent("", keyEventDict.dictionary);
     }
     TIP.flushPendingComposition(keyEvent, keyEventDict.flags);
   } finally {
@@ -1813,25 +2165,25 @@ function synthesizeCompositionChange(aEvent, aWindow = window, aCallback)
 }
 
 // Must be synchronized with nsIDOMWindowUtils.
-const QUERY_CONTENT_FLAG_USE_NATIVE_LINE_BREAK          = 0x0000;
-const QUERY_CONTENT_FLAG_USE_XP_LINE_BREAK              = 0x0001;
+const QUERY_CONTENT_FLAG_USE_NATIVE_LINE_BREAK = 0x0000;
+const QUERY_CONTENT_FLAG_USE_XP_LINE_BREAK = 0x0001;
 
-const QUERY_CONTENT_FLAG_SELECTION_NORMAL                    = 0x0000;
-const QUERY_CONTENT_FLAG_SELECTION_SPELLCHECK                = 0x0002;
-const QUERY_CONTENT_FLAG_SELECTION_IME_RAWINPUT              = 0x0004;
-const QUERY_CONTENT_FLAG_SELECTION_IME_SELECTEDRAWTEXT       = 0x0008;
-const QUERY_CONTENT_FLAG_SELECTION_IME_CONVERTEDTEXT         = 0x0010;
+const QUERY_CONTENT_FLAG_SELECTION_NORMAL = 0x0000;
+const QUERY_CONTENT_FLAG_SELECTION_SPELLCHECK = 0x0002;
+const QUERY_CONTENT_FLAG_SELECTION_IME_RAWINPUT = 0x0004;
+const QUERY_CONTENT_FLAG_SELECTION_IME_SELECTEDRAWTEXT = 0x0008;
+const QUERY_CONTENT_FLAG_SELECTION_IME_CONVERTEDTEXT = 0x0010;
 const QUERY_CONTENT_FLAG_SELECTION_IME_SELECTEDCONVERTEDTEXT = 0x0020;
-const QUERY_CONTENT_FLAG_SELECTION_ACCESSIBILITY             = 0x0040;
-const QUERY_CONTENT_FLAG_SELECTION_FIND                      = 0x0080;
-const QUERY_CONTENT_FLAG_SELECTION_URLSECONDARY              = 0x0100;
-const QUERY_CONTENT_FLAG_SELECTION_URLSTRIKEOUT              = 0x0200;
+const QUERY_CONTENT_FLAG_SELECTION_ACCESSIBILITY = 0x0040;
+const QUERY_CONTENT_FLAG_SELECTION_FIND = 0x0080;
+const QUERY_CONTENT_FLAG_SELECTION_URLSECONDARY = 0x0100;
+const QUERY_CONTENT_FLAG_SELECTION_URLSTRIKEOUT = 0x0200;
 
-const QUERY_CONTENT_FLAG_OFFSET_RELATIVE_TO_INSERTION_POINT  = 0x0400;
+const QUERY_CONTENT_FLAG_OFFSET_RELATIVE_TO_INSERTION_POINT = 0x0400;
 
-const SELECTION_SET_FLAG_USE_NATIVE_LINE_BREAK          = 0x0000;
-const SELECTION_SET_FLAG_USE_XP_LINE_BREAK              = 0x0001;
-const SELECTION_SET_FLAG_REVERSE                        = 0x0002;
+const SELECTION_SET_FLAG_USE_NATIVE_LINE_BREAK = 0x0000;
+const SELECTION_SET_FLAG_USE_XP_LINE_BREAK = 0x0001;
+const SELECTION_SET_FLAG_REVERSE = 0x0002;
 
 /**
  * Synthesize a query text content event.
@@ -1846,8 +2198,7 @@ const SELECTION_SET_FLAG_REVERSE                        = 0x0002;
  * @return         An nsIQueryContentEventResult object.  If this failed,
  *                 the result might be null.
  */
-function synthesizeQueryTextContent(aOffset, aLength, aIsRelative, aWindow)
-{
+function synthesizeQueryTextContent(aOffset, aLength, aIsRelative, aWindow) {
   var utils = _getDOMWindowUtils(aWindow);
   if (!utils) {
     return nullptr;
@@ -1856,8 +2207,14 @@ function synthesizeQueryTextContent(aOffset, aLength, aIsRelative, aWindow)
   if (aIsRelative === true) {
     flags |= QUERY_CONTENT_FLAG_OFFSET_RELATIVE_TO_INSERTION_POINT;
   }
-  return utils.sendQueryContentEvent(utils.QUERY_TEXT_CONTENT,
-                                     aOffset, aLength, 0, 0, flags);
+  return utils.sendQueryContentEvent(
+    utils.QUERY_TEXT_CONTENT,
+    aOffset,
+    aLength,
+    0,
+    0,
+    flags
+  );
 }
 
 /**
@@ -1870,8 +2227,7 @@ function synthesizeQueryTextContent(aOffset, aLength, aIsRelative, aWindow)
  * @return         An nsIQueryContentEventResult object.  If this failed,
  *                 the result might be null.
  */
-function synthesizeQuerySelectedText(aSelectionType, aWindow)
-{
+function synthesizeQuerySelectedText(aSelectionType, aWindow) {
   var utils = _getDOMWindowUtils(aWindow);
   if (!utils) {
     return null;
@@ -1882,8 +2238,14 @@ function synthesizeQuerySelectedText(aSelectionType, aWindow)
     flags |= aSelectionType;
   }
 
-  return utils.sendQueryContentEvent(utils.QUERY_SELECTED_TEXT, 0, 0, 0, 0,
-                                     flags);
+  return utils.sendQueryContentEvent(
+    utils.QUERY_SELECTED_TEXT,
+    0,
+    0,
+    0,
+    0,
+    flags
+  );
 }
 
 /**
@@ -1895,15 +2257,19 @@ function synthesizeQuerySelectedText(aSelectionType, aWindow)
  * @return         An nsIQueryContentEventResult object.  If this failed,
  *                 the result might be null.
  */
-function synthesizeQueryCaretRect(aOffset, aWindow)
-{
+function synthesizeQueryCaretRect(aOffset, aWindow) {
   var utils = _getDOMWindowUtils(aWindow);
   if (!utils) {
     return null;
   }
-  return utils.sendQueryContentEvent(utils.QUERY_CARET_RECT,
-                                     aOffset, 0, 0, 0,
-                                     QUERY_CONTENT_FLAG_USE_NATIVE_LINE_BREAK);
+  return utils.sendQueryContentEvent(
+    utils.QUERY_CARET_RECT,
+    aOffset,
+    0,
+    0,
+    0,
+    QUERY_CONTENT_FLAG_USE_NATIVE_LINE_BREAK
+  );
 }
 
 /**
@@ -1918,8 +2284,7 @@ function synthesizeQueryCaretRect(aOffset, aWindow)
  * @param aWindow  Optional (If null, current |window| will be used)
  * @return         True, if succeeded.  Otherwise false.
  */
-function synthesizeSelectionSet(aOffset, aLength, aReverse, aWindow)
-{
+function synthesizeSelectionSet(aOffset, aLength, aReverse, aWindow) {
   var utils = _getDOMWindowUtils(aWindow);
   if (!utils) {
     return false;
@@ -1937,13 +2302,16 @@ function synthesizeSelectionSet(aOffset, aLength, aReverse, aWindow)
  * when the library or any of function are not found, or something goes wrong
  * in native functions.
  */
-function synthesizeNativeOSXClick(x, y)
-{
+function synthesizeNativeOSXClick(x, y) {
   var { ctypes } = _EU_Cu.import("resource://gre/modules/ctypes.jsm", {});
 
   // Library
-  var CoreFoundation = ctypes.open("/System/Library/Frameworks/CoreFoundation.framework/CoreFoundation");
-  var CoreGraphics = ctypes.open("/System/Library/Frameworks/CoreGraphics.framework/CoreGraphics");
+  var CoreFoundation = ctypes.open(
+    "/System/Library/Frameworks/CoreFoundation.framework/CoreFoundation"
+  );
+  var CoreGraphics = ctypes.open(
+    "/System/Library/Frameworks/CoreGraphics.framework/CoreGraphics"
+  );
 
   // Contants
   var kCGEventLeftMouseDown = 1;
@@ -1963,36 +2331,48 @@ function synthesizeNativeOSXClick(x, y)
   var CGFloat = ctypes.voidptr_t.size == 4 ? ctypes.float : ctypes.double;
   var CGMouseButton = ctypes.uint32_t;
 
-  var CGPoint = new ctypes.StructType(
-    "CGPoint",
-    [ { "x" : CGFloat },
-      { "y" : CGFloat } ]);
+  var CGPoint = new ctypes.StructType("CGPoint", [
+    { x: CGFloat },
+    { y: CGFloat },
+  ]);
 
   // Functions
   var CGEventSourceCreate = CoreGraphics.declare(
     "CGEventSourceCreate",
     ctypes.default_abi,
-    CGEventSourceRef, CGEventSourceStateID);
+    CGEventSourceRef,
+    CGEventSourceStateID
+  );
   var CGEventCreateMouseEvent = CoreGraphics.declare(
     "CGEventCreateMouseEvent",
     ctypes.default_abi,
     CGEventRef,
-    CGEventSourceRef, CGEventType, CGPoint, CGMouseButton);
+    CGEventSourceRef,
+    CGEventType,
+    CGPoint,
+    CGMouseButton
+  );
   var CGEventSetIntegerValueField = CoreGraphics.declare(
     "CGEventSetIntegerValueField",
     ctypes.default_abi,
     ctypes.void_t,
-    CGEventRef, CGEventField, ctypes.int64_t);
+    CGEventRef,
+    CGEventField,
+    ctypes.int64_t
+  );
   var CGEventPost = CoreGraphics.declare(
     "CGEventPost",
     ctypes.default_abi,
     ctypes.void_t,
-    CGEventTapLocation, CGEventRef);
+    CGEventTapLocation,
+    CGEventRef
+  );
   var CFRelease = CoreFoundation.declare(
     "CFRelease",
     ctypes.default_abi,
     ctypes.void_t,
-    CGEventRef);
+    CGEventRef
+  );
 
   var source = CGEventSourceCreate(kCGEventSourceStateHIDSystemState);
   if (!source) {
@@ -2000,23 +2380,37 @@ function synthesizeNativeOSXClick(x, y)
   }
 
   var loc = new CGPoint({ x: x, y: y });
-  var event = CGEventCreateMouseEvent(source, kCGEventLeftMouseDown, loc,
-                                      kCGMouseButtonLeft);
+  var event = CGEventCreateMouseEvent(
+    source,
+    kCGEventLeftMouseDown,
+    loc,
+    kCGMouseButtonLeft
+  );
   if (!event) {
     throw new Error("CGEventCreateMouseEvent returns null");
   }
-  CGEventSetIntegerValueField(event, kCGMouseEventClickState,
-                              new ctypes.Int64(1));
+  CGEventSetIntegerValueField(
+    event,
+    kCGMouseEventClickState,
+    new ctypes.Int64(1)
+  );
   CGEventPost(kCGHIDEventTap, event);
   CFRelease(event);
 
-  event = CGEventCreateMouseEvent(source, kCGEventLeftMouseUp, loc,
-                                      kCGMouseButtonLeft);
+  event = CGEventCreateMouseEvent(
+    source,
+    kCGEventLeftMouseUp,
+    loc,
+    kCGMouseButtonLeft
+  );
   if (!event) {
     throw new Error("CGEventCreateMouseEvent returns null");
   }
-  CGEventSetIntegerValueField(event, kCGMouseEventClickState,
-                              new ctypes.Int64(1));
+  CGEventSetIntegerValueField(
+    event,
+    kCGMouseEventClickState,
+    new ctypes.Int64(1)
+  );
   CGEventPost(kCGHIDEventTap, event);
   CFRelease(event);
 
@@ -2026,78 +2420,6 @@ function synthesizeNativeOSXClick(x, y)
   CoreGraphics.close();
 }
 
-/**
- * Emulate a dragstart event.
- *  element - element to fire the dragstart event on
- *  expectedDragData - the data you expect the data transfer to contain afterwards
- *                      This data is in the format:
- *                         [ [ {type: value, data: value, test: function}, ... ], ... ]
- *                     can be null
- *  aWindow - optional; defaults to the current window object.
- *  x - optional; initial x coordinate
- *  y - optional; initial y coordinate
- * Returns null if data matches.
- * Returns the event.dataTransfer if data does not match
- *
- * eqTest is an optional function if comparison can't be done with x == y;
- *   function (actualData, expectedData) {return boolean}
- *   @param actualData from dataTransfer
- *   @param expectedData from expectedDragData
- * see bug 462172 for example of use
- *
- */
-function synthesizeDragStart(element, expectedDragData, aWindow, x, y)
-{
-  if (!aWindow)
-    aWindow = window;
-  x = x || 2;
-  y = y || 2;
-  const step = 9;
-
-  var result = "trapDrag was not called";
-  var trapDrag = function(event) {
-    try {
-      // We must wrap only in plain mochitests, not chrome
-      var dataTransfer = _EU_maybeWrap(event.dataTransfer);
-      result = null;
-      if (!dataTransfer)
-        throw "no dataTransfer";
-      if (expectedDragData == null ||
-          dataTransfer.mozItemCount != expectedDragData.length)
-        throw dataTransfer;
-      for (var i = 0; i < dataTransfer.mozItemCount; i++) {
-        var dtTypes = dataTransfer.mozTypesAt(i);
-        if (dtTypes.length != expectedDragData[i].length)
-          throw dataTransfer;
-        for (var j = 0; j < dtTypes.length; j++) {
-          if (dtTypes[j] != expectedDragData[i][j].type)
-            throw dataTransfer;
-          var dtData = dataTransfer.mozGetDataAt(dtTypes[j],i);
-          if (expectedDragData[i][j].eqTest) {
-            if (!expectedDragData[i][j].eqTest(dtData, expectedDragData[i][j].data))
-              throw dataTransfer;
-          }
-          else if (expectedDragData[i][j].data != dtData)
-            throw dataTransfer;
-        }
-      }
-    } catch(ex) {
-      result = ex;
-    }
-    event.preventDefault();
-    event.stopPropagation();
-  }
-  aWindow.addEventListener("dragstart", trapDrag);
-  synthesizeMouse(element, x, y, { type: "mousedown" }, aWindow);
-  x += step; y += step;
-  synthesizeMouse(element, x, y, { type: "mousemove" }, aWindow);
-  x += step; y += step;
-  synthesizeMouse(element, x, y, { type: "mousemove" }, aWindow);
-  aWindow.removeEventListener("dragstart", trapDrag);
-  synthesizeMouse(element, x, y, { type: "mouseup" }, aWindow);
-  return result;
-}
-
 /**
  * Synthesize a query text rect event.
  *
@@ -2109,15 +2431,19 @@ function synthesizeDragStart(element, expectedDragData, aWindow, x, y)
  * @return         An nsIQueryContentEventResult object.  If this failed,
  *                 the result might be null.
  */
-function synthesizeQueryTextRect(aOffset, aLength, aWindow)
-{
+function synthesizeQueryTextRect(aOffset, aLength, aWindow) {
   var utils = _getDOMWindowUtils(aWindow);
   if (!utils) {
     return nullptr;
   }
-  return utils.sendQueryContentEvent(utils.QUERY_TEXT_RECT,
-                                     aOffset, aLength, 0, 0,
-                                     QUERY_CONTENT_FLAG_USE_NATIVE_LINE_BREAK);
+  return utils.sendQueryContentEvent(
+    utils.QUERY_TEXT_RECT,
+    aOffset,
+    aLength,
+    0,
+    0,
+    QUERY_CONTENT_FLAG_USE_NATIVE_LINE_BREAK
+  );
 }
 
 /**
@@ -2131,15 +2457,19 @@ function synthesizeQueryTextRect(aOffset, aLength, aWindow)
  * @return         An nsIQueryContentEventResult object.  If this failed,
  *                 the result might be null.
  */
-function synthesizeQueryTextRectArray(aOffset, aLength, aWindow)
-{
+function synthesizeQueryTextRectArray(aOffset, aLength, aWindow) {
   var utils = _getDOMWindowUtils(aWindow);
   if (!utils) {
     return nullptr;
   }
-  return utils.sendQueryContentEvent(utils.QUERY_TEXT_RECT_ARRAY,
-                                     aOffset, aLength, 0, 0,
-                                     QUERY_CONTENT_FLAG_USE_NATIVE_LINE_BREAK);
+  return utils.sendQueryContentEvent(
+    utils.QUERY_TEXT_RECT_ARRAY,
+    aOffset,
+    aLength,
+    0,
+    0,
+    QUERY_CONTENT_FLAG_USE_NATIVE_LINE_BREAK
+  );
 }
 
 /**
@@ -2149,14 +2479,19 @@ function synthesizeQueryTextRectArray(aOffset, aLength, aWindow)
  * @return         An nsIQueryContentEventResult object.  If this failed,
  *                 the result might be null.
  */
-function synthesizeQueryEditorRect(aWindow)
-{
+function synthesizeQueryEditorRect(aWindow) {
   var utils = _getDOMWindowUtils(aWindow);
   if (!utils) {
     return nullptr;
   }
-  return utils.sendQueryContentEvent(utils.QUERY_EDITOR_RECT, 0, 0, 0, 0,
-                                     QUERY_CONTENT_FLAG_USE_NATIVE_LINE_BREAK);
+  return utils.sendQueryContentEvent(
+    utils.QUERY_EDITOR_RECT,
+    0,
+    0,
+    0,
+    0,
+    QUERY_CONTENT_FLAG_USE_NATIVE_LINE_BREAK
+  );
 }
 
 /**
@@ -2167,15 +2502,19 @@ function synthesizeQueryEditorRect(aWindow)
  * @return         An nsIQueryContentEventResult object.  If this failed,
  *                 the result might be null.
  */
-function synthesizeCharAtPoint(aX, aY, aWindow)
-{
+function synthesizeCharAtPoint(aX, aY, aWindow) {
   var utils = _getDOMWindowUtils(aWindow);
   if (!utils) {
     return nullptr;
   }
-  return utils.sendQueryContentEvent(utils.QUERY_CHARACTER_AT_POINT,
-                                     0, 0, aX, aY,
-                                     QUERY_CONTENT_FLAG_USE_NATIVE_LINE_BREAK);
+  return utils.sendQueryContentEvent(
+    utils.QUERY_CHARACTER_AT_POINT,
+    0,
+    0,
+    aX,
+    aY,
+    QUERY_CONTENT_FLAG_USE_NATIVE_LINE_BREAK
+  );
 }
 
 /**
@@ -2191,9 +2530,13 @@ function synthesizeCharAtPoint(aX, aY, aWindow)
  *                       object
  * @return               An object to pass to sendDragEvent.
  */
-function createDragEventObject(aType, aDestElement, aDestWindow, aDataTransfer,
-                               aDragEvent)
-{
+function createDragEventObject(
+  aType,
+  aDestElement,
+  aDestWindow,
+  aDataTransfer,
+  aDragEvent
+) {
   var destRect = aDestElement.getBoundingClientRect();
   var destClientX = destRect.left + destRect.width / 2;
   var destClientY = destRect.top + destRect.height / 2;
@@ -2250,8 +2593,15 @@ function createDragEventObject(aType, aDestElement, aDestWindow, aDataTransfer,
  *                      dragover event, and the second element is the
  *                      dataTransfer for the current drag session.
  */
-function synthesizeDragOver(aSrcElement, aDestElement, aDragData, aDropEffect, aWindow, aDestWindow, aDragEvent={})
-{
+function synthesizeDragOver(
+  aSrcElement,
+  aDestElement,
+  aDragData,
+  aDropEffect,
+  aWindow,
+  aDestWindow,
+  aDragEvent = {}
+) {
   if (!aWindow) {
     aWindow = window;
   }
@@ -2259,8 +2609,12 @@ function synthesizeDragOver(aSrcElement, aDestElement, aDragData, aDropEffect, a
     aDestWindow = aWindow;
   }
 
-  const obs = _EU_Cc["@mozilla.org/observer-service;1"].getService(_EU_Ci.nsIObserverService);
-  const ds = _EU_Cc["@mozilla.org/widget/dragservice;1"].getService(_EU_Ci.nsIDragService);
+  const obs = _EU_Cc["@mozilla.org/observer-service;1"].getService(
+    _EU_Ci.nsIObserverService
+  );
+  const ds = _EU_Cc["@mozilla.org/widget/dragservice;1"].getService(
+    _EU_Ci.nsIDragService
+  );
   var sess = ds.getCurrentSession();
 
   // This method runs before other callbacks, and acts as a way to inject the
@@ -2270,7 +2624,11 @@ function synthesizeDragOver(aSrcElement, aDestElement, aDragData, aDropEffect, a
       for (var i = 0; i < aDragData.length; i++) {
         var item = aDragData[i];
         for (var j = 0; j < item.length; j++) {
-          _EU_maybeWrap(event.dataTransfer).mozSetDataAt(item[j].type, item[j].data, i);
+          _EU_maybeWrap(event.dataTransfer).mozSetDataAt(
+            item[j].type,
+            item[j].data,
+            i
+          );
         }
       }
     }
@@ -2280,7 +2638,9 @@ function synthesizeDragOver(aSrcElement, aDestElement, aDragData, aDropEffect, a
 
   function trapDrag(subject, topic) {
     if (topic == "on-datatransfer-available") {
-      sess.dataTransfer = _EU_maybeUnwrap(_EU_maybeWrap(subject).mozCloneForEvent("drop"));
+      sess.dataTransfer = _EU_maybeUnwrap(
+        _EU_maybeWrap(subject).mozCloneForEvent("drop")
+      );
       sess.dataTransfer.dropEffect = subject.dropEffect;
     }
   }
@@ -2294,7 +2654,7 @@ function synthesizeDragOver(aSrcElement, aDestElement, aDragData, aDropEffect, a
   var x = rect.width / 2;
   var y = rect.height / 2;
   synthesizeMouse(aSrcElement, x, y, { type: "mousemove" }, aWindow);
-  synthesizeMouse(aSrcElement, x+10, y+10, { type: "mousemove" }, aWindow);
+  synthesizeMouse(aSrcElement, x + 10, y + 10, { type: "mousemove" }, aWindow);
   aWindow.removeEventListener("dragstart", fillDrag, true);
   obs.removeObserver(trapDrag, "on-datatransfer-available");
 
@@ -2304,8 +2664,13 @@ function synthesizeDragOver(aSrcElement, aDestElement, aDragData, aDropEffect, a
   }
 
   // The EventStateManager will fire our dragenter event if it needs to.
-  var event = createDragEventObject("dragover", aDestElement, aDestWindow,
-                                    dataTransfer, aDragEvent);
+  var event = createDragEventObject(
+    "dragover",
+    aDestElement,
+    aDestWindow,
+    dataTransfer,
+    aDragEvent
+  );
   var result = sendDragEvent(event, aDestElement, aDestWindow);
 
   return [result, dataTransfer];
@@ -2326,8 +2691,13 @@ function synthesizeDragOver(aSrcElement, aDestElement, aDragData, aDropEffect, a
  * @return               "none" if aResult is true,
  *                       aDataTransfer.dropEffect otherwise.
  */
-function synthesizeDropAfterDragOver(aResult, aDataTransfer, aDestElement, aDestWindow, aDragEvent={})
-{
+function synthesizeDropAfterDragOver(
+  aResult,
+  aDataTransfer,
+  aDestElement,
+  aDestWindow,
+  aDragEvent = {}
+) {
   if (!aDestWindow) {
     aDestWindow = window;
   }
@@ -2338,8 +2708,13 @@ function synthesizeDropAfterDragOver(aResult, aDataTransfer, aDestElement, aDest
   if (aResult) {
     effect = "none";
   } else if (effect != "none") {
-    event = createDragEventObject("drop", aDestElement, aDestWindow,
-                                  aDataTransfer, aDragEvent);
+    event = createDragEventObject(
+      "drop",
+      aDestElement,
+      aDestWindow,
+      aDataTransfer,
+      aDragEvent
+    );
     sendDragEvent(event, aDestElement, aDestWindow);
   }
   synthesizeMouse(aDestElement, 2, 2, { type: "mouseup" }, aDestWindow);
@@ -2367,8 +2742,15 @@ function synthesizeDropAfterDragOver(aResult, aDataTransfer, aDestElement, aDest
  *                      passed to sendDragEvent.
  * @return              The drop effect that was desired.
  */
-function synthesizeDrop(aSrcElement, aDestElement, aDragData, aDropEffect, aWindow, aDestWindow, aDragEvent={})
-{
+function synthesizeDrop(
+  aSrcElement,
+  aDestElement,
+  aDragData,
+  aDropEffect,
+  aWindow,
+  aDestWindow,
+  aDragEvent = {}
+) {
   if (!aWindow) {
     aWindow = window;
   }
@@ -2376,8 +2758,9 @@ function synthesizeDrop(aSrcElement, aDestElement, aDragData, aDropEffect, aWind
     aDestWindow = aWindow;
   }
 
-  var ds = _EU_Cc["@mozilla.org/widget/dragservice;1"]
-           .getService(_EU_Ci.nsIDragService);
+  var ds = _EU_Cc["@mozilla.org/widget/dragservice;1"].getService(
+    _EU_Ci.nsIDragService
+  );
 
   let dropAction;
   switch (aDropEffect) {
@@ -2399,17 +2782,40 @@ function synthesizeDrop(aSrcElement, aDestElement, aDragData, aDropEffect, aWind
   ds.startDragSessionForTests(dropAction);
 
   try {
-    var [result, dataTransfer] = synthesizeDragOver(aSrcElement, aDestElement,
-                                                    aDragData, aDropEffect,
-                                                    aWindow, aDestWindow,
-                                                    aDragEvent);
-    return synthesizeDropAfterDragOver(result, dataTransfer, aDestElement,
-                                       aDestWindow, aDragEvent);
+    var [result, dataTransfer] = synthesizeDragOver(
+      aSrcElement,
+      aDestElement,
+      aDragData,
+      aDropEffect,
+      aWindow,
+      aDestWindow,
+      aDragEvent
+    );
+    return synthesizeDropAfterDragOver(
+      result,
+      dataTransfer,
+      aDestElement,
+      aDestWindow,
+      aDragEvent
+    );
   } finally {
     ds.endDragSession(true, _parseModifiers(aDragEvent));
   }
 }
 
+function _computeSrcElementFromSrcSelection(aSrcSelection) {
+  let srcElement = aSrcSelection.focusNode;
+  while (_EU_maybeWrap(srcElement).isNativeAnonymous) {
+    srcElement = _EU_maybeUnwrap(
+      _EU_maybeWrap(srcElement).flattenedTreeParentNode
+    );
+  }
+  if (srcElement.nodeType !== Node.NODE_TYPE_ELEMENT) {
+    srcElement = srcElement.parentElement;
+  }
+  return srcElement;
+}
+
 /**
  * Emulate a drag and drop by emulating a dragstart by mousedown and mousemove,
  * and firing events dragenter, dragover, drop, and dragend.
@@ -2480,15 +2886,7 @@ async function synthesizePlainDragAndDrop(aParams) {
   }
 
   if (srcSelection) {
-    srcElement = srcSelection.focusNode;
-    while (_EU_maybeWrap(srcElement).isNativeAnonymous) {
-      srcElement = _EU_maybeUnwrap(
-        _EU_maybeWrap(srcElement).flattenedTreeParentNode
-      );
-    }
-    if (srcElement.nodeType !== Node.NODE_TYPE_ELEMENT) {
-      srcElement = srcElement.parentElement;
-    }
+    srcElement = _computeSrcElementFromSrcSelection(srcSelection);
     let srcElementRect = srcElement.getBoundingClientRect();
     if (logFunc) {
       logFunc(
@@ -2506,21 +2904,13 @@ async function synthesizePlainDragAndDrop(aParams) {
       );
     }
     // Click at center of last selection rect.
-    srcX = Math.floor(
-      lastSelectionRect.left + lastSelectionRect.width / 2
-    );
-    srcY = Math.floor(
-      lastSelectionRect.top + lastSelectionRect.height / 2
-    );
+    srcX = Math.floor(lastSelectionRect.left + lastSelectionRect.width / 2);
+    srcY = Math.floor(lastSelectionRect.top + lastSelectionRect.height / 2);
     // Then, adjust srcX and srcY for making them offset relative to
     // srcElementRect because they will be used when we call synthesizeMouse()
     // with srcElement.
-    srcX = Math.floor(
-      srcX - srcElementRect.left
-    );
-    srcY = Math.floor(
-      srcY - srcElementRect.top
-    );
+    srcX = Math.floor(srcX - srcElementRect.left);
+    srcY = Math.floor(srcY - srcElementRect.top);
     // Finally, recalculate finalX and finalY with new srcX and srcY if they
     // are not specified by the caller.
     if (aParams.finalX === undefined) {
@@ -2557,7 +2947,11 @@ async function synthesizePlainDragAndDrop(aParams) {
       if (logFunc) {
         logFunc(`"${aEvent.type}" event is fired`);
       }
-      if (!srcElement.contains(aEvent.target)) {
+      if (
+        !srcElement.contains(
+          _EU_maybeUnwrap(_EU_maybeWrap(aEvent).composedTarget)
+        )
+      ) {
         // If srcX and srcY does not point in one of rects in srcElement,
         // "dragstart" target is not in srcElement.  Such case must not
         // be expected by this API users so that we should throw an exception
@@ -2613,7 +3007,13 @@ async function synthesizePlainDragAndDrop(aParams) {
     let session = ds.getCurrentSession();
     if (!session) {
       if (expectCancelDragStart) {
-        synthesizeMouse(srcElement, srcX, srcY, { type: "mouseup" }, srcWindow);
+        synthesizeMouse(
+          srcElement,
+          finalX,
+          finalY,
+          { type: "mouseup" },
+          srcWindow
+        );
         return;
       }
       throw new Error("drag hasn't been started by the operation");
@@ -2721,7 +3121,11 @@ async function synthesizePlainDragAndDrop(aParams) {
           if (logFunc) {
             logFunc(`"${aEvent.type}" event is fired`);
           }
-          if (!destElement.contains(aEvent.target)) {
+          if (
+            !destElement.contains(
+              _EU_maybeUnwrap(_EU_maybeWrap(aEvent).composedTarget)
+            )
+          ) {
             throw new Error(
               'event target of "drop" is not destElement nor its descendant'
             );
@@ -2770,9 +3174,13 @@ async function synthesizePlainDragAndDrop(aParams) {
         if (logFunc) {
           logFunc(`"${aEvent.type}" event is fired`);
         }
-        if (!srcElement.contains(aEvent.target)) {
+        if (
+          !srcElement.contains(
+            _EU_maybeUnwrap(_EU_maybeWrap(aEvent).composedTarget)
+          )
+        ) {
           throw new Error(
-            'event target of "dragend" is not srcElement not its descendant'
+            'event target of "dragend" is not srcElement nor its descendant'
           );
         }
       }
@@ -2796,6 +3204,106 @@ async function synthesizePlainDragAndDrop(aParams) {
   }
 }
 
+function _checkDataTransferItems(aDataTransfer, aExpectedDragData) {
+  try {
+    // We must wrap only in plain mochitests, not chrome
+    let dataTransfer = _EU_maybeWrap(aDataTransfer);
+    if (!dataTransfer) {
+      return null;
+    }
+    if (
+      aExpectedDragData == null ||
+      dataTransfer.mozItemCount != aExpectedDragData.length
+    ) {
+      return dataTransfer;
+    }
+    for (let i = 0; i < dataTransfer.mozItemCount; i++) {
+      let dtTypes = dataTransfer.mozTypesAt(i);
+      if (dtTypes.length != aExpectedDragData[i].length) {
+        return dataTransfer;
+      }
+      for (let j = 0; j < dtTypes.length; j++) {
+        if (dtTypes[j] != aExpectedDragData[i][j].type) {
+          return dataTransfer;
+        }
+        let dtData = dataTransfer.mozGetDataAt(dtTypes[j], i);
+        if (aExpectedDragData[i][j].eqTest) {
+          if (
+            !aExpectedDragData[i][j].eqTest(
+              dtData,
+              aExpectedDragData[i][j].data
+            )
+          ) {
+            return dataTransfer;
+          }
+        } else if (aExpectedDragData[i][j].data != dtData) {
+          return dataTransfer;
+        }
+      }
+    }
+  } catch (ex) {
+    return ex;
+  }
+  return true;
+}
+
+/**
+ * synthesizePlainDragAndCancel() synthesizes drag start with
+ * synthesizePlainDragAndDrop(), but always cancel it with preventing default
+ * of "dragstart".  Additionally, this checks whether the dataTransfer of
+ * "dragstart" event has only expected items.
+ *
+ * @param aParams       The params which is set to the argument of
+ *                      synthesizePlainDragAndDrop().
+ * @param aExpectedDataTransferItems
+ *                      All expected dataTransfer items.
+ *                      This data is in the format:
+ *                         [ [ {type: value, data: value, test: function}, ... ], ... ]
+ *                      can be null.
+ *                      eqTest is an optional function if comparison can't be
+ *                      done with x == y;
+ *                      function (actualData, expectedData) {return boolean}
+ * @return              true if aExpectedDataTransferItems matches with
+ *                      DragEvent.dataTransfer of "dragstart" event.
+ *                      Otherwise, the dataTransfer object (may be null) or
+ *                      thrown exception, NOT false.  Therefore, you shouldn't
+ *                      use
+ */
+async function synthesizePlainDragAndCancel(
+  aParams,
+  aExpectedDataTransferItems
+) {
+  let srcElement = aParams.srcSelection
+    ? _computeSrcElementFromSrcSelection(aParams.srcSelection)
+    : aParams.srcElement;
+  let result;
+  function onDragStart(aEvent) {
+    aEvent.preventDefault();
+    result = _checkDataTransferItems(
+      aEvent.dataTransfer,
+      aExpectedDataTransferItems
+    );
+  }
+  SpecialPowers.addSystemEventListener(
+    srcElement.ownerDocument,
+    "dragstart",
+    onDragStart,
+    { capture: true }
+  );
+  try {
+    aParams.expectCancelDragStart = true;
+    await synthesizePlainDragAndDrop(aParams);
+  } finally {
+    SpecialPowers.removeSystemEventListener(
+      srcElement.ownerDocument,
+      "dragstart",
+      onDragStart,
+      { capture: true }
+    );
+  }
+  return result;
+}
+
 var PluginUtils = {
   withTestPlugin: function(callback) {
     var ph = _EU_Cc["@mozilla.org/plugin/host;1"].getService(
@@ -2812,7 +3320,7 @@ var PluginUtils = {
     }
     todo(false, "Need a test plugin on this platform");
     return false;
-  }
+  },
 };
 
 class EventCounter {
@@ -2826,14 +3334,17 @@ class EventCounter {
     // SpecialPowers is picky and needs to be passed an explicit reference to
     // the function to be called. To avoid having to bind "this", we therefore
     // define the method this way, via a property.
-    this.handleEvent = (aEvent) => {
-        this.eventCount++;
+    this.handleEvent = aEvent => {
+      this.eventCount++;
     };
 
     if (aOptions.mozSystemGroup) {
-      SpecialPowers.addSystemEventListener(aTarget, aType,
-                                           this.handleEvent,
-                                           aOptions.capture);
+      SpecialPowers.addSystemEventListener(
+        aTarget,
+        aType,
+        this.handleEvent,
+        aOptions.capture
+      );
     } else {
       aTarget.addEventListener(aType, this, aOptions);
     }
@@ -2841,9 +3352,12 @@ class EventCounter {
 
   unregister() {
     if (this.options.mozSystemGroup) {
-      SpecialPowers.removeSystemEventListener(this.target, this.type,
-                                              this.handleEvent,
-                                              this.options.capture);
+      SpecialPowers.removeSystemEventListener(
+        this.target,
+        this.type,
+        this.handleEvent,
+        this.options.capture
+      );
     } else {
       this.target.removeEventListener(this.type, this, this.options);
     }
diff --git a/testing/mochitest/tests/SimpleTest/ExtensionTestUtils.js b/testing/mochitest/tests/SimpleTest/ExtensionTestUtils.js
index e5f5e672bf..9a37dda8a1 100644
--- a/testing/mochitest/tests/SimpleTest/ExtensionTestUtils.js
+++ b/testing/mochitest/tests/SimpleTest/ExtensionTestUtils.js
@@ -138,4 +138,18 @@ ExtensionTestUtils.loadExtension = function(ext)
 
   SimpleTest.info(`Extension loaded`);
   return extension;
-}
+};
+
+ExtensionTestUtils.failOnSchemaWarnings = (warningsAsErrors = true) => {
+  let prefName = "extensions.webextensions.warnings-as-errors";
+  SpecialPowers.setBoolPref(prefName, warningsAsErrors);
+  if (!warningsAsErrors) {
+    let registerCleanup;
+    if (typeof registerCleanupFunction != "undefined") {
+      registerCleanup = registerCleanupFunction;
+    } else {
+      registerCleanup = SimpleTest.registerCleanupFunction.bind(SimpleTest);
+    }
+    registerCleanup(() => SpecialPowers.setBoolPref(prefName, true));
+  }
+};
diff --git a/testing/mochitest/tests/SimpleTest/SimpleTest.js b/testing/mochitest/tests/SimpleTest/SimpleTest.js
index 71050b1913..04acde3934 100644
--- a/testing/mochitest/tests/SimpleTest/SimpleTest.js
+++ b/testing/mochitest/tests/SimpleTest/SimpleTest.js
@@ -31,8 +31,8 @@ try {
 // case it is not defined) from a parent/opener window.
 //
 // Finding the SpecialPowers object is needed when we have ChromePowers in
-// harness.xul and we need SpecialPowers in the iframe, and also for tests
-// like test_focus.xul where we open a window which opens another window which
+// harness.xhtml and we need SpecialPowers in the iframe, and also for tests
+// like test_focus.xhtml where we open a window which opens another window which
 // includes SimpleTest.js.
 (function() {
     function ancestor(w) {
diff --git a/testing/mochitest/tests/browser/dummy.html b/testing/mochitest/tests/browser/dummy.html
index af0a303d6b..7954185285 100644
--- a/testing/mochitest/tests/browser/dummy.html
+++ b/testing/mochitest/tests/browser/dummy.html
@@ -1,6 +1,6 @@
 <!DOCTYPE html>
 <html>
-  <meta http-equiv="Content-Security-Policy" content="default-src 'none'"></meta>
+  <meta http-equiv="Content-Security-Policy" content="default-src 'none'; object-src 'none'"></meta>
   <title>This is a dummy page</title>
   <meta charset="utf-8">
   <body>This is a dummy page</body>
diff --git a/testing/mozbase/mozrunner/mozrunner/utils.py b/testing/mozbase/mozrunner/mozrunner/utils.py
index a4c0ac10d1..c7a7fef1c1 100644
--- a/testing/mozbase/mozrunner/mozrunner/utils.py
+++ b/testing/mozbase/mozrunner/mozrunner/utils.py
@@ -141,6 +141,9 @@ def test_environment(xrePath, env=None, crashreporter=True, debugger=False,
     env.setdefault('R_LOG_DESTINATION', 'stderr')
     env.setdefault('R_LOG_VERBOSE', '1')
 
+    # Ask NSS to use lower-security password encryption. See Bug 1594559
+    env.setdefault('NSS_MAX_MP_PBE_ITERATION_COUNT', '10')
+
     # ASan specific environment stuff
     asan = bool(mozinfo.info.get("asan"))
     if asan:
diff --git a/testing/mozharness/configs/unittests/linux_unittest.py b/testing/mozharness/configs/unittests/linux_unittest.py
index e50c9fc625..fd850e4101 100644
--- a/testing/mozharness/configs/unittests/linux_unittest.py
+++ b/testing/mozharness/configs/unittests/linux_unittest.py
@@ -169,7 +169,6 @@ config = {
         "mochitest-browser-chrome-chunked": ["--flavor=browser", "--chunk-by-runtime"],
         "mochitest-browser-chrome-coverage": ["--flavor=browser", "--chunk-by-runtime", "--timeout=1200"],
         "mochitest-browser-chrome-screenshots": ["--flavor=browser", "--subsuite=screenshots"],
-        "mochitest-browser-chrome-instrumentation": ["--flavor=browser"],
         "mochitest-webgl1-core": ["--subsuite=webgl1-core"],
         "mochitest-webgl1-ext": ["--subsuite=webgl1-ext"],
         "mochitest-webgl2-core": ["--subsuite=webgl2-core"],
diff --git a/testing/mozharness/configs/unittests/mac_unittest.py b/testing/mozharness/configs/unittests/mac_unittest.py
index 339bc15f92..70c766a519 100644
--- a/testing/mozharness/configs/unittests/mac_unittest.py
+++ b/testing/mozharness/configs/unittests/mac_unittest.py
@@ -136,7 +136,6 @@ config = {
         "mochitest-browser-chrome": ["--flavor=browser"],
         "mochitest-browser-chrome-chunked": ["--flavor=browser", "--chunk-by-runtime"],
         "mochitest-browser-chrome-screenshots": ["--flavor=browser", "--subsuite=screenshots"],
-        "mochitest-browser-chrome-instrumentation": ["--flavor=browser"],
         "mochitest-webgl1-core": ["--subsuite=webgl1-core"],
         "mochitest-webgl1-ext": ["--subsuite=webgl1-ext"],
         "mochitest-webgl2-core": ["--subsuite=webgl2-core"],
diff --git a/testing/mozharness/configs/unittests/win_unittest.py b/testing/mozharness/configs/unittests/win_unittest.py
index faf346df4d..1243d7ea60 100644
--- a/testing/mozharness/configs/unittests/win_unittest.py
+++ b/testing/mozharness/configs/unittests/win_unittest.py
@@ -159,7 +159,6 @@ config = {
         "mochitest-browser-chrome": ["--flavor=browser"],
         "mochitest-browser-chrome-chunked": ["--flavor=browser", "--chunk-by-runtime"],
         "mochitest-browser-chrome-screenshots": ["--flavor=browser", "--subsuite=screenshots"],
-        "mochitest-browser-chrome-instrumentation": ["--flavor=browser"],
         "mochitest-webgl1-core": ["--subsuite=webgl1-core"],
         "mochitest-webgl1-ext": ["--subsuite=webgl1-ext"],
         "mochitest-webgl2-core": ["--subsuite=webgl2-core"],
diff --git a/testing/mozharness/mozharness/mozilla/testing/codecoverage.py b/testing/mozharness/mozharness/mozilla/testing/codecoverage.py
index eb6e89eecf..dd2c219f15 100644
--- a/testing/mozharness/mozharness/mozilla/testing/codecoverage.py
+++ b/testing/mozharness/mozharness/mozilla/testing/codecoverage.py
@@ -188,8 +188,8 @@ class CodeCoverageMixin(SingleTestMixin):
                 'test': 'testing/mochitest/baselinecoverage/browser_chrome/browser_baselinecoverage.js',  # NOQA: E501
                 'suite': 'mochitest-browser-chrome'
             },
-            '.xul': {
-                'test': 'testing/mochitest/baselinecoverage/chrome/test_baselinecoverage.xul',
+            '.xhtml': {
+                'test': 'testing/mochitest/baselinecoverage/chrome/test_baselinecoverage.xhtml',
                 'suite': 'mochitest-chrome'
             }
         }
diff --git a/testing/profiles/common/user.js b/testing/profiles/common/user.js
index d437af8d0b..0dd93be49d 100644
--- a/testing/profiles/common/user.js
+++ b/testing/profiles/common/user.js
@@ -57,4 +57,3 @@ user_pref("media.allowed-to-play.enabled", true);
 // Ensure media can always play without delay
 user_pref("media.block-autoplay-until-in-foreground", false);
 user_pref("toolkit.telemetry.coverage.endpoint.base", "http://localhost");
-user_pref("layout.css.moz-binding.content.enabled", true); // Le sad
diff --git a/testing/profiles/raptor-android/user.js b/testing/profiles/raptor-android/user.js
index aa523ba134..d3caf91cfe 100644
--- a/testing/profiles/raptor-android/user.js
+++ b/testing/profiles/raptor-android/user.js
@@ -3,3 +3,7 @@
 
 // disk cache smart size is enabled in shipped apps
 user_pref("browser.cache.disk.smart_size.enabled", true);
+
+// Raptor's manifest.json contains the "geckoProfiler" permission, which is
+// not supported on Android. Ignore the warning about the unknown permission.
+user_pref("extensions.webextensions.warnings-as-errors", false);
diff --git a/testing/talos/talos/pageloader/api.js b/testing/talos/talos/pageloader/api.js
index d440f2a292..3edff1c89b 100644
--- a/testing/talos/talos/pageloader/api.js
+++ b/testing/talos/talos/pageloader/api.js
@@ -61,9 +61,9 @@ XPCOMUtils.defineLazyServiceGetter(
 );
 
 async function talosStart() {
-  // Tests are driven from pageloader.xul.  We need to be careful to open
-  // pageloader.xul before dismissing the default browser window or we
-  // may inadvertently cause the browser to exit before the pageloader.xul
+  // Tests are driven from pageloader.xhtml.  We need to be careful to open
+  // pageloader.xhtml before dismissing the default browser window or we
+  // may inadvertently cause the browser to exit before the pageloader.xhtml
   // window is opened.  Start by finding or waiting for the default window.
   let defaultWin = Services.wm.getMostRecentWindow("navigator:browser");
   if (!defaultWin) {
@@ -84,8 +84,8 @@ async function talosStart() {
   }
 
   // Wwe've got the default window, it is time for pageloader to take over.
-  // Open pageloader.xul in a new window and then close the default window.
-  let chromeURL = "chrome://pageloader/content/pageloader.xul";
+  // Open pageloader.xhtml in a new window and then close the default window.
+  let chromeURL = "chrome://pageloader/content/pageloader.xhtml";
 
   let args = {};
   args.wrappedJSObject = args;
diff --git a/testing/talos/talos/pageloader/chrome/pageloader.xul b/testing/talos/talos/pageloader/chrome/pageloader.xhtml
similarity index 100%
rename from testing/talos/talos/pageloader/chrome/pageloader.xul
rename to testing/talos/talos/pageloader/chrome/pageloader.xhtml
diff --git a/testing/talos/talos/startup_test/sessionrestore/profile/sessionstore.js b/testing/talos/talos/startup_test/sessionrestore/profile/sessionstore.js
index acd7b93c87..2ea238ef85 100644
--- a/testing/talos/talos/startup_test/sessionrestore/profile/sessionstore.js
+++ b/testing/talos/talos/startup_test/sessionrestore/profile/sessionstore.js
@@ -6193,9 +6193,6 @@
     "startTime": 1393256133774,
     "recentCrashes": 0
   },
-  "scratchpads": [
-    
-  ],
   "global": {
     
   }
diff --git a/testing/talos/talos/talos-powers/api.js b/testing/talos/talos/talos-powers/api.js
index 7077554a7b..c8e6cfa0dc 100644
--- a/testing/talos/talos/talos-powers/api.js
+++ b/testing/talos/talos/talos-powers/api.js
@@ -265,21 +265,8 @@ TalosPowersService.prototype = {
     // down, since some caching that can influence future runs in this profile
     // keys off of that notification.
     let topWin = BrowserWindowTracker.getTopWindow();
-    if (
-      topWin &&
-      topWin.gBrowserInit &&
-      !topWin.gBrowserInit.idleTasksFinished
-    ) {
-      await new Promise(resolve => {
-        let obs = (subject, topic, data) => {
-          Services.obs.removeObserver(
-            obs,
-            "browser-idle-startup-tasks-finished"
-          );
-          resolve();
-        };
-        Services.obs.addObserver(obs, "browser-idle-startup-tasks-finished");
-      });
+    if (topWin && topWin.gBrowserInit) {
+      await topWin.gBrowserInit.idleTasksFinishedPromise;
     }
 
     for (let domWindow of Services.wm.getEnumerator(null)) {
diff --git a/testing/talos/talos/tests/devtools/addon/api.js b/testing/talos/talos/tests/devtools/addon/api.js
index 159c598e09..1faee44a0d 100644
--- a/testing/talos/talos/tests/devtools/addon/api.js
+++ b/testing/talos/talos/tests/devtools/addon/api.js
@@ -13,7 +13,7 @@ this.damp = class extends ExtensionAPI {
       damp: {
         startTest() {
           let { rootURI } = context.extension;
-          let window = context.xulWindow;
+          let window = context.appWindow;
           if (!("Damp" in window)) {
             let script = rootURI.resolve("content/damp.js");
             Services.scriptloader.loadSubScript(script, window);
diff --git a/testing/talos/talos/tests/tart/addon/content/tab-min-width-1px.css b/testing/talos/talos/tests/tart/addon/content/tab-min-width-1px.css
index 9de7857053..994ced11dd 100644
--- a/testing/talos/talos/tests/tart/addon/content/tab-min-width-1px.css
+++ b/testing/talos/talos/tests/tart/addon/content/tab-min-width-1px.css
@@ -2,7 +2,7 @@
 
 /*
 Overlay this style rule at tart/chrome.manifest (but it seems to regress tab perf):
-style chrome://browser/content/browser.xul chrome://tart/content/tab-min-width-1px.css
+style chrome://browser/content/browser.xhtml chrome://tart/content/tab-min-width-1px.css
 */
 
 /* Prevent overflow while adding many tabs */
diff --git a/testing/talos/talos/tests/tart/addon/content/tart.js b/testing/talos/talos/tests/tart/addon/content/tart.js
index b42d4ba81c..62d6f4449b 100644
--- a/testing/talos/talos/tests/tart/addon/content/tart.js
+++ b/testing/talos/talos/tests/tart/addon/content/tart.js
@@ -128,10 +128,10 @@ Tart.prototype = {
     this._endDetection = this.tabDetector;
     this._win.BrowserOpenTab();
     // Modifying the style for each tab right after opening seems like it could regress performance,
-    // However, overlaying a global style over browser.xul actually ends up having greater ovrehead,
+    // However, overlaying a global style over browser.xhtml actually ends up having greater ovrehead,
     // especially while closing the last of many tabs (a noticeable ~250ms delay before expanding the rest).
     // To overlay the style globally, add at tart/chrome.manifest:
-    // style chrome://browser/content/browser.xul chrome://tart/content/tab-min-width-1px.css
+    // style chrome://browser/content/browser.xhtml chrome://tart/content/tab-min-width-1px.css
     // where the file tab-min-width-1px.css is:
     // .tabbrowser-tab[fadein]:not([pinned]) { min-width: 1px !important; }
     // Additionally, the global style overlay apparently messes with intervals recording when layout.frame_rate=10000:
@@ -480,17 +480,6 @@ Tart.prototype = {
       }
     }
 
-    function getReferenceCustomizationDuration() {
-      // Code by jaws.
-      try {
-        let deck = document.getElementById("content-deck");
-        let cstyle = window.getComputedStyle(deck);
-        return 1000 * parseFloat(cstyle.transitionDuration, 10);
-      } catch (e) {
-        return 150; // Value at the time of writing
-      }
-    }
-
     this.unpinTart();
     var tabRefDuration = getMaxTabTransitionTimeMs(this._tartTab);
     if (tabRefDuration < 20 || tabRefDuration > 2000) {
@@ -498,7 +487,7 @@ Tart.prototype = {
       tabRefDuration = 250;
     }
 
-    var custRefDuration = getReferenceCustomizationDuration();
+    var custRefDuration = 0;
 
     var subtests = {
       init: [
diff --git a/testing/talos/talos/tests/twinopen/api.js b/testing/talos/talos/tests/twinopen/api.js
index f8949e66f7..3cfcc17b45 100644
--- a/testing/talos/talos/tests/twinopen/api.js
+++ b/testing/talos/talos/tests/twinopen/api.js
@@ -55,7 +55,7 @@ async function startTest(context) {
   Cu.forceGC();
   Cu.forceCC();
   Cu.forceShrinkingGC();
-  let win = context.xulWindow;
+  let win = context.appWindow;
   await openDelay(win);
   let mozAfterPaint = waitForBrowserPaint();
 
diff --git a/testing/talos/talos/xtalos/xperf_whitelist.json b/testing/talos/talos/xtalos/xperf_whitelist.json
index d272675151..c0050f0936 100644
--- a/testing/talos/talos/xtalos/xperf_whitelist.json
+++ b/testing/talos/talos/xtalos/xperf_whitelist.json
@@ -374,7 +374,7 @@
     "minbytes": 0,
     "maxbytes": 127000
   },
-  "{profile}\\extensions\\pageloader@mozilla.org\\chrome\\pageloader.xul": {
+  "{profile}\\extensions\\pageloader@mozilla.org\\chrome\\pageloader.xhtml": {
     "mincount": 0,
     "maxcount": 4,
     "minbytes": 0,
diff --git a/testing/web-platform/meta/2dcontext/drawing-paths-to-the-canvas/drawFocusIfNeeded_001.html.ini b/testing/web-platform/meta/2dcontext/drawing-paths-to-the-canvas/drawFocusIfNeeded_001.html.ini
deleted file mode 100644
index 11b94b7614..0000000000
--- a/testing/web-platform/meta/2dcontext/drawing-paths-to-the-canvas/drawFocusIfNeeded_001.html.ini
+++ /dev/null
@@ -1,7 +0,0 @@
-[drawFocusIfNeeded_001.html]
-  disabled:
-    if (os == "win"): https://bugzilla.mozilla.org/show_bug.cgi?id=1092458
-  [drawFocusIfNeeded draws a focus ring.]
-    expected:
-      if not debug and (os == "win") and (version == "6.1.7601"): FAIL
-
diff --git a/testing/web-platform/meta/2dcontext/drawing-paths-to-the-canvas/drawFocusIfNeeded_004.html.ini b/testing/web-platform/meta/2dcontext/drawing-paths-to-the-canvas/drawFocusIfNeeded_004.html.ini
deleted file mode 100644
index 1022a802b5..0000000000
--- a/testing/web-platform/meta/2dcontext/drawing-paths-to-the-canvas/drawFocusIfNeeded_004.html.ini
+++ /dev/null
@@ -1,7 +0,0 @@
-[drawFocusIfNeeded_004.html]
-  disabled:
-    if (os == "win"): https://bugzilla.mozilla.org/show_bug.cgi?id=1092458
-  [drawFocusIfNeeded does draw a focus ring if the element is in focus.]
-    expected:
-      if not debug and (os == "win") and (version == "6.1.7601"): FAIL
-
diff --git a/testing/web-platform/meta/2dcontext/drawing-paths-to-the-canvas/drawFocusIfNeeded_005.html.ini b/testing/web-platform/meta/2dcontext/drawing-paths-to-the-canvas/drawFocusIfNeeded_005.html.ini
deleted file mode 100644
index af8c6a2645..0000000000
--- a/testing/web-platform/meta/2dcontext/drawing-paths-to-the-canvas/drawFocusIfNeeded_005.html.ini
+++ /dev/null
@@ -1,7 +0,0 @@
-[drawFocusIfNeeded_005.html]
-  disabled:
-    if (os == "win"): https://bugzilla.mozilla.org/show_bug.cgi?id=1092458
-  [drawFocusIfNeeded does draw a focus ring if the element is in focus and the user activated a particular focus ring.]
-    expected:
-      if not debug and (os == "win") and (version == "6.1.7601"): FAIL
-
diff --git a/testing/web-platform/meta/css/CSS2/bidi-text/bidi-001.xht.ini b/testing/web-platform/meta/css/CSS2/bidi-text/bidi-001.xht.ini
index f5aab79f77..daa1701436 100644
--- a/testing/web-platform/meta/css/CSS2/bidi-text/bidi-001.xht.ini
+++ b/testing/web-platform/meta/css/CSS2/bidi-text/bidi-001.xht.ini
@@ -1,3 +1,4 @@
 [bidi-001.xht]
   fuzzy:
-    if os == "mac": maxDifference=3;totalPixels=0-1
+    if os == "win": maxDifference=1;totalPixels=0-2
+    if os == "mac": maxDifference=1-3;totalPixels=0-1
diff --git a/testing/web-platform/meta/css/CSS2/bidi-text/bidi-002.xht.ini b/testing/web-platform/meta/css/CSS2/bidi-text/bidi-002.xht.ini
index a606245391..c0b1af53ce 100644
--- a/testing/web-platform/meta/css/CSS2/bidi-text/bidi-002.xht.ini
+++ b/testing/web-platform/meta/css/CSS2/bidi-text/bidi-002.xht.ini
@@ -1,3 +1,4 @@
 [bidi-002.xht]
   fuzzy:
+    if os == "win": maxDifference=1;totalPixels=0-4
     if os == "mac": maxDifference=1;totalPixels=0-1
diff --git a/testing/web-platform/meta/css/CSS2/bidi-text/bidi-box-model-003.xht.ini b/testing/web-platform/meta/css/CSS2/bidi-text/bidi-box-model-003.xht.ini
new file mode 100644
index 0000000000..7843964b31
--- /dev/null
+++ b/testing/web-platform/meta/css/CSS2/bidi-text/bidi-box-model-003.xht.ini
@@ -0,0 +1,3 @@
+[bidi-box-model-003.xht]
+  fuzzy:
+    if os == "win": maxDifference=1;totalPixels=0-1
diff --git a/testing/web-platform/meta/css/css-flexbox/__dir__.ini b/testing/web-platform/meta/css/css-flexbox/__dir__.ini
new file mode 100644
index 0000000000..daf68383df
--- /dev/null
+++ b/testing/web-platform/meta/css/css-flexbox/__dir__.ini
@@ -0,0 +1 @@
+leak-threshold: [default:51200]
diff --git a/testing/web-platform/meta/css/css-grid/table-grid-item-dynamic-004.html.ini b/testing/web-platform/meta/css/css-grid/table-grid-item-dynamic-004.html.ini
index e4e567f894..f0022447e1 100644
--- a/testing/web-platform/meta/css/css-grid/table-grid-item-dynamic-004.html.ini
+++ b/testing/web-platform/meta/css/css-grid/table-grid-item-dynamic-004.html.ini
@@ -1,3 +1,5 @@
 [table-grid-item-dynamic-004.html]
-  expected: FAIL
+  expected:
+    if (os == "android"): ["FAIL", "PASS"]
+    FAIL
   bug: https://bugzilla.mozilla.org/show_bug.cgi?id=1521088
diff --git a/testing/web-platform/meta/css/css-pseudo/selection-input-011.html.ini b/testing/web-platform/meta/css/css-pseudo/selection-input-011.html.ini
new file mode 100644
index 0000000000..7944d13272
--- /dev/null
+++ b/testing/web-platform/meta/css/css-pseudo/selection-input-011.html.ini
@@ -0,0 +1,2 @@
+[selection-input-011.html]
+  expected: FAIL
diff --git a/testing/web-platform/meta/css/css-pseudo/selection-intercharacter-011.html.ini b/testing/web-platform/meta/css/css-pseudo/selection-intercharacter-011.html.ini
new file mode 100644
index 0000000000..b13c25f03d
--- /dev/null
+++ b/testing/web-platform/meta/css/css-pseudo/selection-intercharacter-011.html.ini
@@ -0,0 +1,2 @@
+[selection-intercharacter-011.html]
+  expected: FAIL
diff --git a/testing/web-platform/meta/css/css-pseudo/selection-intercharacter-012.html.ini b/testing/web-platform/meta/css/css-pseudo/selection-intercharacter-012.html.ini
new file mode 100644
index 0000000000..7fb41423e2
--- /dev/null
+++ b/testing/web-platform/meta/css/css-pseudo/selection-intercharacter-012.html.ini
@@ -0,0 +1,2 @@
+[selection-intercharacter-012.html]
+  expected: FAIL
diff --git a/testing/web-platform/meta/css/css-pseudo/selection-textarea-011.html.ini b/testing/web-platform/meta/css/css-pseudo/selection-textarea-011.html.ini
new file mode 100644
index 0000000000..dcd69f7918
--- /dev/null
+++ b/testing/web-platform/meta/css/css-pseudo/selection-textarea-011.html.ini
@@ -0,0 +1,5 @@
+[selection-textarea-011.html]
+  expected:
+    if (os == "linux") and webrender: PASS
+    if os == "android": PASS
+    FAIL
diff --git a/testing/web-platform/meta/css/css-text/boundary-shaping/boundary-shaping-010.html.ini b/testing/web-platform/meta/css/css-text/boundary-shaping/boundary-shaping-010.html.ini
deleted file mode 100644
index f8792199a5..0000000000
--- a/testing/web-platform/meta/css/css-text/boundary-shaping/boundary-shaping-010.html.ini
+++ /dev/null
@@ -1,5 +0,0 @@
-[boundary-shaping-010.html]
-  expected:
-    if os == "mac": FAIL
-    if (os == "android") and not e10s: FAIL
-    if (os == "android") and e10s: FAIL
diff --git a/testing/web-platform/meta/css/css-text/shaping/shaping_lig-000.html.ini b/testing/web-platform/meta/css/css-text/shaping/shaping_lig-000.html.ini
deleted file mode 100644
index da1688c4a8..0000000000
--- a/testing/web-platform/meta/css/css-text/shaping/shaping_lig-000.html.ini
+++ /dev/null
@@ -1,4 +0,0 @@
-[shaping_lig-000.html]
-  expected:
-    if (os == "android") and not e10s: FAIL
-    if (os == "android") and e10s: FAIL
diff --git a/testing/web-platform/meta/css/selectors/__dir__.ini b/testing/web-platform/meta/css/selectors/__dir__.ini
index 7ba3fce839..9e805240a9 100644
--- a/testing/web-platform/meta/css/selectors/__dir__.ini
+++ b/testing/web-platform/meta/css/selectors/__dir__.ini
@@ -1 +1,2 @@
-prefs: [layout.css.focus-visible.enabled:true]
+lsan-disabled: true
+leak-threshold: [default:3276800, tab:460800]
diff --git a/testing/web-platform/meta/css/selectors/focus-visible-003.html.ini b/testing/web-platform/meta/css/selectors/focus-visible-003.html.ini
new file mode 100644
index 0000000000..c5a4a0fd77
--- /dev/null
+++ b/testing/web-platform/meta/css/selectors/focus-visible-003.html.ini
@@ -0,0 +1,6 @@
+[focus-visible-003.html]
+  expected:
+    if os == "android": TIMEOUT
+  [Mouse focus on input elements which do not show a virtual keyboard should NOT match :focus-visible]
+    expected:
+      if os == "android": TIMEOUT
diff --git a/testing/web-platform/meta/css/selectors/focus-visible-005.html.ini b/testing/web-platform/meta/css/selectors/focus-visible-005.html.ini
index 563afabdec..9f5934867c 100644
--- a/testing/web-platform/meta/css/selectors/focus-visible-005.html.ini
+++ b/testing/web-platform/meta/css/selectors/focus-visible-005.html.ini
@@ -1,3 +1,2 @@
 [focus-visible-005.html]
-  [Programmatic focus after click should not match :focus-visible]
-    expected: FAIL
+  prefs: [accessibility.mouse_focuses_formcontrol:true]
diff --git a/testing/web-platform/meta/html/canvas/element/drawing-paths-to-the-canvas/drawFocusIfNeeded_001.html.ini b/testing/web-platform/meta/html/canvas/element/drawing-paths-to-the-canvas/drawFocusIfNeeded_001.html.ini
deleted file mode 100644
index a842a1078d..0000000000
--- a/testing/web-platform/meta/html/canvas/element/drawing-paths-to-the-canvas/drawFocusIfNeeded_001.html.ini
+++ /dev/null
@@ -1,5 +0,0 @@
-[drawFocusIfNeeded_001.html]
-  [drawFocusIfNeeded draws a focus ring.]
-    expected:
-      if (os == "win") or (os == "linux"): FAIL
-
diff --git a/testing/web-platform/meta/html/canvas/element/drawing-paths-to-the-canvas/drawFocusIfNeeded_004.html.ini b/testing/web-platform/meta/html/canvas/element/drawing-paths-to-the-canvas/drawFocusIfNeeded_004.html.ini
deleted file mode 100644
index 0a379d0d8e..0000000000
--- a/testing/web-platform/meta/html/canvas/element/drawing-paths-to-the-canvas/drawFocusIfNeeded_004.html.ini
+++ /dev/null
@@ -1,5 +0,0 @@
-[drawFocusIfNeeded_004.html]
-  [drawFocusIfNeeded does draw a focus ring if the element is in focus.]
-    expected:
-      if (os == "win") or (os == "linux"): FAIL
-
diff --git a/testing/web-platform/meta/html/canvas/element/drawing-paths-to-the-canvas/drawFocusIfNeeded_005.html.ini b/testing/web-platform/meta/html/canvas/element/drawing-paths-to-the-canvas/drawFocusIfNeeded_005.html.ini
deleted file mode 100644
index e3251936d6..0000000000
--- a/testing/web-platform/meta/html/canvas/element/drawing-paths-to-the-canvas/drawFocusIfNeeded_005.html.ini
+++ /dev/null
@@ -1,5 +0,0 @@
-[drawFocusIfNeeded_005.html]
-  [drawFocusIfNeeded does draw a focus ring if the element is in focus and the user activated a particular focus ring.]
-    expected:
-      if (os == "win") or (os == "linux"): FAIL
-
diff --git a/testing/web-platform/meta/html/semantics/text-level-semantics/the-bdo-element/bdo-child.html.ini b/testing/web-platform/meta/html/semantics/text-level-semantics/the-bdo-element/bdo-child.html.ini
new file mode 100644
index 0000000000..342262bb9b
--- /dev/null
+++ b/testing/web-platform/meta/html/semantics/text-level-semantics/the-bdo-element/bdo-child.html.ini
@@ -0,0 +1,3 @@
+[bdo-child.html]
+  fuzzy:
+    if os == "win": maxDifference=1;totalPixels=0-2
diff --git a/testing/web-platform/meta/html/semantics/text-level-semantics/the-bdo-element/bidi-001.html.ini b/testing/web-platform/meta/html/semantics/text-level-semantics/the-bdo-element/bidi-001.html.ini
new file mode 100644
index 0000000000..6b4c115141
--- /dev/null
+++ b/testing/web-platform/meta/html/semantics/text-level-semantics/the-bdo-element/bidi-001.html.ini
@@ -0,0 +1,3 @@
+[bidi-001.html]
+  fuzzy:
+    if os == "win": maxDifference=1;totalPixels=0-2
diff --git a/testing/web-platform/meta/longtask-timing/buffered-flag.window.js.ini b/testing/web-platform/meta/longtask-timing/buffered-flag.window.js.ini
new file mode 100644
index 0000000000..f26edb697f
--- /dev/null
+++ b/testing/web-platform/meta/longtask-timing/buffered-flag.window.js.ini
@@ -0,0 +1,4 @@
+[buffered-flag.window.html]
+  [PerformanceObserver with buffered flag can see previous longtask entries.]
+    expected: FAIL
+
diff --git a/testing/web-platform/meta/longtask-timing/containerTypes.html.ini b/testing/web-platform/meta/longtask-timing/containerTypes.html.ini
new file mode 100644
index 0000000000..5784671b3c
--- /dev/null
+++ b/testing/web-platform/meta/longtask-timing/containerTypes.html.ini
@@ -0,0 +1,13 @@
+[containerTypes.html]
+  [Performance longtask entries in frame are observable in parent.]
+    expected: FAIL
+
+  [Performance longtask entries in iframe are observable in parent.]
+    expected: FAIL
+
+  [Performance longtask entries in object are observable in parent.]
+    expected: FAIL
+
+  [Performance longtask entries in embed are observable in parent.]
+    expected: FAIL
+
diff --git a/testing/web-platform/meta/longtask-timing/idlharness.window.js.ini b/testing/web-platform/meta/longtask-timing/idlharness.window.js.ini
index a10f83c4a5..b0e889503d 100644
--- a/testing/web-platform/meta/longtask-timing/idlharness.window.js.ini
+++ b/testing/web-platform/meta/longtask-timing/idlharness.window.js.ini
@@ -1,7 +1,4 @@
 [idlharness.window.html]
-  [longtasks interfaces]
-    expected: FAIL
-
   [PerformanceLongTaskTiming interface: existence and properties of interface object]
     expected: FAIL
 
diff --git a/testing/web-platform/meta/longtask-timing/long-microtask.window.js.ini b/testing/web-platform/meta/longtask-timing/long-microtask.window.js.ini
new file mode 100644
index 0000000000..d6dd191c7f
--- /dev/null
+++ b/testing/web-platform/meta/longtask-timing/long-microtask.window.js.ini
@@ -0,0 +1,4 @@
+[long-microtask.window.html]
+  [A short task followed by a long microtask is observable.]
+    expected: FAIL
+
diff --git a/testing/web-platform/meta/longtask-timing/longtask-attributes.html.ini b/testing/web-platform/meta/longtask-timing/longtask-attributes.html.ini
index ee2f2bc788..c89e31fffd 100644
--- a/testing/web-platform/meta/longtask-timing/longtask-attributes.html.ini
+++ b/testing/web-platform/meta/longtask-timing/longtask-attributes.html.ini
@@ -1,7 +1,4 @@
 [longtask-attributes.html]
-  [Performance longtask entries are observable]
-    expected: TIMEOUT
-
   [Performance longtask entries are observable.]
     expected: FAIL
 
diff --git a/testing/web-platform/meta/longtask-timing/longtask-in-childiframe-crossorigin.html.ini b/testing/web-platform/meta/longtask-timing/longtask-in-childiframe-crossorigin.html.ini
index 7d9bd896aa..210f7c8956 100644
--- a/testing/web-platform/meta/longtask-timing/longtask-in-childiframe-crossorigin.html.ini
+++ b/testing/web-platform/meta/longtask-timing/longtask-in-childiframe-crossorigin.html.ini
@@ -1,10 +1,4 @@
 [longtask-in-childiframe-crossorigin.html]
-  [Performance longtask entries in child iframe are observable in parent]
-    expected: TIMEOUT
-
-  [Performance longtask entries in child iframe are observable in parent.]
-    expected: TIMEOUT
-
   [Performance longtask entries in cross-origin child iframe are observable in parent.]
     expected: FAIL
 
diff --git a/testing/web-platform/meta/longtask-timing/longtask-in-childiframe.html.ini b/testing/web-platform/meta/longtask-timing/longtask-in-childiframe.html.ini
index 6ed6c9a255..948d248081 100644
--- a/testing/web-platform/meta/longtask-timing/longtask-in-childiframe.html.ini
+++ b/testing/web-platform/meta/longtask-timing/longtask-in-childiframe.html.ini
@@ -1,7 +1,4 @@
 [longtask-in-childiframe.html]
-  [Performance longtask entries in child iframe are observable in parent]
-    expected: TIMEOUT
-
   [Performance longtask entries in child iframe are observable in parent.]
     expected: FAIL
 
diff --git a/testing/web-platform/meta/longtask-timing/longtask-in-externalscript.html.ini b/testing/web-platform/meta/longtask-timing/longtask-in-externalscript.html.ini
index 52cf2a56a2..cac68566f9 100644
--- a/testing/web-platform/meta/longtask-timing/longtask-in-externalscript.html.ini
+++ b/testing/web-platform/meta/longtask-timing/longtask-in-externalscript.html.ini
@@ -1,7 +1,4 @@
 [longtask-in-externalscript.html]
-  [Performance longtask entries are observable]
-    expected: TIMEOUT
-
   [Performance longtask entries are observable.]
     expected: FAIL
 
diff --git a/testing/web-platform/meta/longtask-timing/longtask-in-parentiframe.html.ini b/testing/web-platform/meta/longtask-timing/longtask-in-parentiframe.html.ini
index 829d408592..538861b88e 100644
--- a/testing/web-platform/meta/longtask-timing/longtask-in-parentiframe.html.ini
+++ b/testing/web-platform/meta/longtask-timing/longtask-in-parentiframe.html.ini
@@ -1,7 +1,4 @@
 [longtask-in-parentiframe.html]
-  [Performance longtask entries in parent are observable in child iframe]
-    expected: TIMEOUT
-
   [Performance longtask entries in parent are observable in child iframe.]
     expected: FAIL
 
diff --git a/testing/web-platform/meta/longtask-timing/longtask-in-raf.html.ini b/testing/web-platform/meta/longtask-timing/longtask-in-raf.html.ini
index 08e2425de7..76ec6bce89 100644
--- a/testing/web-platform/meta/longtask-timing/longtask-in-raf.html.ini
+++ b/testing/web-platform/meta/longtask-timing/longtask-in-raf.html.ini
@@ -1,7 +1,4 @@
 [longtask-in-raf.html]
-  [Performance longtask entries are observable]
-    expected: TIMEOUT
-
   [Performance longtask entries are observable.]
     expected: FAIL
 
diff --git a/testing/web-platform/meta/longtask-timing/longtask-in-sibling-iframe-crossorigin.html.ini b/testing/web-platform/meta/longtask-timing/longtask-in-sibling-iframe-crossorigin.html.ini
index 9ba436d009..fafcab34a6 100644
--- a/testing/web-platform/meta/longtask-timing/longtask-in-sibling-iframe-crossorigin.html.ini
+++ b/testing/web-platform/meta/longtask-timing/longtask-in-sibling-iframe-crossorigin.html.ini
@@ -1,10 +1,4 @@
 [longtask-in-sibling-iframe-crossorigin.html]
-  [Performance longtask entries in parent are observable in child iframe]
-    expected: TIMEOUT
-
-  [Performance longtask entries in parent are observable in child iframe.]
-    expected: TIMEOUT
-
   [Performance longtask entries from cross-origin iframe are observable in its sibling.]
     expected: FAIL
 
diff --git a/testing/web-platform/meta/longtask-timing/longtask-in-sibling-iframe.html.ini b/testing/web-platform/meta/longtask-timing/longtask-in-sibling-iframe.html.ini
index 0a64d966f7..be7e3a8b3b 100644
--- a/testing/web-platform/meta/longtask-timing/longtask-in-sibling-iframe.html.ini
+++ b/testing/web-platform/meta/longtask-timing/longtask-in-sibling-iframe.html.ini
@@ -1,10 +1,4 @@
 [longtask-in-sibling-iframe.html]
-  [Performance longtask entries in parent are observable in child iframe]
-    expected: TIMEOUT
-
-  [Performance longtask entries in parent are observable in child iframe.]
-    expected: TIMEOUT
-
   [Performance longtask entries are observable in sibling iframe.]
     expected: FAIL
 
diff --git a/testing/web-platform/meta/longtask-timing/supported-longtask-types.window.js.ini b/testing/web-platform/meta/longtask-timing/supported-longtask-types.window.js.ini
index c38d339fc3..9602301122 100644
--- a/testing/web-platform/meta/longtask-timing/supported-longtask-types.window.js.ini
+++ b/testing/web-platform/meta/longtask-timing/supported-longtask-types.window.js.ini
@@ -2,3 +2,6 @@
   [supportedEntryTypes contains 'longtask' but not 'taskattribution'.]
     expected: FAIL
 
+  ['longtask' entries should be observable.]
+    expected: FAIL
+
diff --git a/testing/web-platform/meta/mathml/presentation-markup/direction/direction-008.html.ini b/testing/web-platform/meta/mathml/presentation-markup/direction/direction-008.html.ini
new file mode 100644
index 0000000000..a9fdbdc5e9
--- /dev/null
+++ b/testing/web-platform/meta/mathml/presentation-markup/direction/direction-008.html.ini
@@ -0,0 +1,3 @@
+[direction-008.html]
+  expected:
+    FAIL
diff --git a/testing/web-platform/meta/mathml/presentation-markup/direction/direction-009.html.ini b/testing/web-platform/meta/mathml/presentation-markup/direction/direction-009.html.ini
new file mode 100644
index 0000000000..2fc904fe51
--- /dev/null
+++ b/testing/web-platform/meta/mathml/presentation-markup/direction/direction-009.html.ini
@@ -0,0 +1,4 @@
+[direction-009.html]
+  expected:
+    FAIL
+  bug: 787215
diff --git a/testing/web-platform/meta/mathml/presentation-markup/fractions/frac-linethickness-001.html.ini b/testing/web-platform/meta/mathml/presentation-markup/fractions/frac-linethickness-001.html.ini
index 46aeafcacd..78c5925789 100644
--- a/testing/web-platform/meta/mathml/presentation-markup/fractions/frac-linethickness-001.html.ini
+++ b/testing/web-platform/meta/mathml/presentation-markup/fractions/frac-linethickness-001.html.ini
@@ -1,2 +1,2 @@
 [frac-linethickness-001.html]
-  expected: FAIL
+  prefs: [mathml.nonzero_unitless_lengths.disabled:true, mathml.mfrac_linethickness_names.disabled:true]
diff --git a/testing/web-platform/meta/mathml/presentation-markup/fractions/frac-parameters-gap-001.html.ini b/testing/web-platform/meta/mathml/presentation-markup/fractions/frac-parameters-gap-001.html.ini
new file mode 100644
index 0000000000..c2b3ad4f8e
--- /dev/null
+++ b/testing/web-platform/meta/mathml/presentation-markup/fractions/frac-parameters-gap-001.html.ini
@@ -0,0 +1,5 @@
+[frac-parameters-gap-001.html]
+  expected:
+    if os == "android": PASS
+    if os == "linux": PASS
+    FAIL
diff --git a/testing/web-platform/meta/mathml/presentation-markup/fractions/frac-parameters-gap-002.html.ini b/testing/web-platform/meta/mathml/presentation-markup/fractions/frac-parameters-gap-002.html.ini
new file mode 100644
index 0000000000..4430d2ae28
--- /dev/null
+++ b/testing/web-platform/meta/mathml/presentation-markup/fractions/frac-parameters-gap-002.html.ini
@@ -0,0 +1,5 @@
+[frac-parameters-gap-002.html]
+  expected:
+    if os == "android": PASS
+    if os == "linux": PASS
+    FAIL
diff --git a/testing/web-platform/meta/mathml/presentation-markup/fractions/frac-parameters-gap-003.html.ini b/testing/web-platform/meta/mathml/presentation-markup/fractions/frac-parameters-gap-003.html.ini
new file mode 100644
index 0000000000..947d833439
--- /dev/null
+++ b/testing/web-platform/meta/mathml/presentation-markup/fractions/frac-parameters-gap-003.html.ini
@@ -0,0 +1,5 @@
+[frac-parameters-gap-003.html]
+  expected:
+    if os == "android": PASS
+    if os == "linux": PASS
+    FAIL
diff --git a/testing/web-platform/meta/mathml/presentation-markup/fractions/frac-parameters-gap-004.html.ini b/testing/web-platform/meta/mathml/presentation-markup/fractions/frac-parameters-gap-004.html.ini
new file mode 100644
index 0000000000..b4775a8c61
--- /dev/null
+++ b/testing/web-platform/meta/mathml/presentation-markup/fractions/frac-parameters-gap-004.html.ini
@@ -0,0 +1,5 @@
+[frac-parameters-gap-004.html]
+  expected:
+    if os == "android": PASS
+    if os == "linux": PASS
+    FAIL
diff --git a/testing/web-platform/meta/mathml/presentation-markup/fractions/frac-parameters-gap-005.html.ini b/testing/web-platform/meta/mathml/presentation-markup/fractions/frac-parameters-gap-005.html.ini
new file mode 100644
index 0000000000..a6cbd77af4
--- /dev/null
+++ b/testing/web-platform/meta/mathml/presentation-markup/fractions/frac-parameters-gap-005.html.ini
@@ -0,0 +1,5 @@
+[frac-parameters-gap-005.html]
+  expected:
+    if os == "linux": PASS
+    if os == "android": PASS
+    FAIL
diff --git a/testing/web-platform/meta/mathml/presentation-markup/fractions/frac-parameters-gap-006.html.ini b/testing/web-platform/meta/mathml/presentation-markup/fractions/frac-parameters-gap-006.html.ini
new file mode 100644
index 0000000000..1be73c008a
--- /dev/null
+++ b/testing/web-platform/meta/mathml/presentation-markup/fractions/frac-parameters-gap-006.html.ini
@@ -0,0 +1,5 @@
+[frac-parameters-gap-006.html]
+  expected:
+    if os == "linux": PASS
+    if os == "android": PASS
+    FAIL
diff --git a/testing/web-platform/meta/mathml/presentation-markup/operators/mo-movablelimits.html.ini b/testing/web-platform/meta/mathml/presentation-markup/operators/mo-movablelimits.html.ini
new file mode 100644
index 0000000000..5d90c0e63d
--- /dev/null
+++ b/testing/web-platform/meta/mathml/presentation-markup/operators/mo-movablelimits.html.ini
@@ -0,0 +1,2 @@
+[mo-movablelimits.html]
+  expected: FAIL
diff --git a/testing/web-platform/meta/mathml/relations/css-styling/attribute-mapping-001.html.ini b/testing/web-platform/meta/mathml/relations/css-styling/attribute-mapping-001.html.ini
new file mode 100644
index 0000000000..a7eb012fc1
--- /dev/null
+++ b/testing/web-platform/meta/mathml/relations/css-styling/attribute-mapping-001.html.ini
@@ -0,0 +1,196 @@
+[attribute-mapping-001.html]
+  [mathsize on the msub element is mapped to CSS font-size]
+    expected: FAIL
+
+  [dir on the msup element is mapped to CSS direction]
+    expected: FAIL
+
+  [mathsize on the mstyle element is mapped to CSS font-size]
+    expected: FAIL
+
+  [dir on the math element is mapped to CSS direction]
+    expected: FAIL
+
+  [dir on the munder element is mapped to CSS direction]
+    expected: FAIL
+
+  [dir on the munderover element is mapped to CSS direction]
+    expected: FAIL
+
+  [mathsize on the maction element is mapped to CSS font-size]
+    expected: FAIL
+
+  [mathsize on the mi element is mapped to CSS font-size]
+    expected: FAIL
+
+  [dir on the mover element is mapped to CSS direction]
+    expected: FAIL
+
+  [mathsize on the mtable element is mapped to CSS font-size]
+    expected: FAIL
+
+  [mathsize on the mn element is mapped to CSS font-size]
+    expected: FAIL
+
+  [dir on the msqrt element is mapped to CSS direction]
+    expected: FAIL
+
+  [dir on the mtr element is mapped to CSS direction]
+    expected: FAIL
+
+  [mathsize on the msqrt element is mapped to CSS font-size]
+    expected: FAIL
+
+  [mathsize on the mrow element is mapped to CSS font-size]
+    expected: FAIL
+
+  [mathsize on the mfrac element is mapped to CSS font-size]
+    expected: FAIL
+
+  [mathsize on the munder element is mapped to CSS font-size]
+    expected: FAIL
+
+  [mathsize on the mtr element is mapped to CSS font-size]
+    expected: FAIL
+
+  [mathsize on the annotation-xml element is mapped to CSS font-size]
+    expected: FAIL
+
+  [mathsize on the none element is mapped to CSS font-size]
+    expected: FAIL
+
+  [dir on the merror element is mapped to CSS direction]
+    expected: FAIL
+
+  [dir on the mfrac element is mapped to CSS direction]
+    expected: FAIL
+
+  [mathsize on the menclose element is mapped to CSS font-size]
+    expected: FAIL
+
+  [mathsize on the mroot element is mapped to CSS font-size]
+    expected: FAIL
+
+  [mathsize on the munderover element is mapped to CSS font-size]
+    expected: FAIL
+
+  [mathcolor on the merror element is mapped to CSS color]
+    expected: FAIL
+
+  [mathsize on the msubsup element is mapped to CSS font-size]
+    expected: FAIL
+
+  [dir on the mtd element is mapped to CSS direction]
+    expected: FAIL
+
+  [mathsize on the mprescripts element is mapped to CSS font-size]
+    expected: FAIL
+
+  [dir on the maction element is mapped to CSS direction]
+    expected: FAIL
+
+  [dir on the annotation-xml element is mapped to CSS direction]
+    expected: FAIL
+
+  [mathsize on the ms element is mapped to CSS font-size]
+    expected: FAIL
+
+  [dir on the mstyle element is mapped to CSS direction]
+    expected: FAIL
+
+  [dir on the mtext element is mapped to CSS direction]
+    expected: FAIL
+
+  [dir on the mspace element is mapped to CSS direction]
+    expected: FAIL
+
+  [dir on the mphantom element is mapped to CSS direction]
+    expected: FAIL
+
+  [dir on the annotation element is mapped to CSS direction]
+    expected: FAIL
+
+  [dir on the none element is mapped to CSS direction]
+    expected: FAIL
+
+  [dir on the mrow element is mapped to CSS direction]
+    expected: FAIL
+
+  [dir on the menclose element is mapped to CSS direction]
+    expected: FAIL
+
+  [mathsize on the mspace element is mapped to CSS font-size]
+    expected: FAIL
+
+  [dir on the mroot element is mapped to CSS direction]
+    expected: FAIL
+
+  [dir on the mo element is mapped to CSS direction]
+    expected: FAIL
+
+  [dir on the mprescripts element is mapped to CSS direction]
+    expected: FAIL
+
+  [mathsize on the math element is mapped to CSS font-size]
+    expected: FAIL
+
+  [mathsize on the mover element is mapped to CSS font-size]
+    expected: FAIL
+
+  [mathsize on the mtd element is mapped to CSS font-size]
+    expected: FAIL
+
+  [mathsize on the merror element is mapped to CSS font-size]
+    expected: FAIL
+
+  [dir on the msub element is mapped to CSS direction]
+    expected: FAIL
+
+  [mathsize on the mmultiscripts element is mapped to CSS font-size]
+    expected: FAIL
+
+  [dir on the mmultiscripts element is mapped to CSS direction]
+    expected: FAIL
+
+  [dir on the mi element is mapped to CSS direction]
+    expected: FAIL
+
+  [dir on the mn element is mapped to CSS direction]
+    expected: FAIL
+
+  [mathsize on the msup element is mapped to CSS font-size]
+    expected: FAIL
+
+  [mathsize on the mphantom element is mapped to CSS font-size]
+    expected: FAIL
+
+  [mathsize on the mo element is mapped to CSS font-size]
+    expected: FAIL
+
+  [dir on the msubsup element is mapped to CSS direction]
+    expected: FAIL
+
+  [mathsize on the mtext element is mapped to CSS font-size]
+    expected: FAIL
+
+  [dir on the ms element is mapped to CSS direction]
+    expected: FAIL
+
+  [dir on the mpadded element is mapped to CSS direction]
+    expected: FAIL
+
+  [mathsize on the annotation element is mapped to CSS font-size]
+    expected: FAIL
+
+  [mathsize on the mpadded element is mapped to CSS font-size]
+    expected: FAIL
+
+  [dir on the mtable element is mapped to CSS direction]
+    expected: FAIL
+
+  [dir on the semantics element is mapped to CSS direction]
+    expected: FAIL
+
+  [mathsize on the semantics element is mapped to CSS font-size]
+    expected: FAIL
+
diff --git a/testing/web-platform/meta/mathml/relations/css-styling/attribute-mapping-002.html.ini b/testing/web-platform/meta/mathml/relations/css-styling/attribute-mapping-002.html.ini
new file mode 100644
index 0000000000..544ed3d046
--- /dev/null
+++ b/testing/web-platform/meta/mathml/relations/css-styling/attribute-mapping-002.html.ini
@@ -0,0 +1,288 @@
+[attribute-mapping-002.html]
+  [displaystyle on the mphantom element is mapped to CSS math-style]
+    expected: FAIL
+
+  [scriptlevel on the munder element is mapped to CSS math-script-level]
+    expected: FAIL
+
+  [scriptlevel on the menclose element is mapped to CSS math-script-level]
+    expected: FAIL
+
+  [displaystyle on the mspace element is mapped to CSS math-style]
+    expected: FAIL
+
+  [displaystyle on the mtd element is mapped to CSS math-style]
+    expected: FAIL
+
+  [mathvariant on the munderover element is mapped to CSS text-transform]
+    expected: FAIL
+
+  [mathvariant on the merror element is mapped to CSS text-transform]
+    expected: FAIL
+
+  [mathvariant on the maction element is mapped to CSS text-transform]
+    expected: FAIL
+
+  [displaystyle on the munderover element is mapped to CSS math-style]
+    expected: FAIL
+
+  [displaystyle on the msup element is mapped to CSS math-style]
+    expected: FAIL
+
+  [displaystyle on the msub element is mapped to CSS math-style]
+    expected: FAIL
+
+  [mathvariant on the munder element is mapped to CSS text-transform]
+    expected: FAIL
+
+  [mathvariant on the mrow element is mapped to CSS text-transform]
+    expected: FAIL
+
+  [scriptlevel on the msqrt element is mapped to CSS math-script-level]
+    expected: FAIL
+
+  [mathvariant on the mo element is mapped to CSS text-transform]
+    expected: FAIL
+
+  [displaystyle on the ms element is mapped to CSS math-style]
+    expected: FAIL
+
+  [mathvariant on the mtr element is mapped to CSS text-transform]
+    expected: FAIL
+
+  [scriptlevel on the munderover element is mapped to CSS math-script-level]
+    expected: FAIL
+
+  [displaystyle on the mtr element is mapped to CSS math-style]
+    expected: FAIL
+
+  [mathvariant on the annotation element is mapped to CSS text-transform]
+    expected: FAIL
+
+  [mathvariant on the mtd element is mapped to CSS text-transform]
+    expected: FAIL
+
+  [displaystyle on the mo element is mapped to CSS math-style]
+    expected: FAIL
+
+  [scriptlevel on the mtable element is mapped to CSS math-script-level]
+    expected: FAIL
+
+  [displaystyle on the maction element is mapped to CSS math-style]
+    expected: FAIL
+
+  [mathvariant on the mpadded element is mapped to CSS text-transform]
+    expected: FAIL
+
+  [displaystyle on the msqrt element is mapped to CSS math-style]
+    expected: FAIL
+
+  [displaystyle on the mstyle element is mapped to CSS math-style]
+    expected: FAIL
+
+  [scriptlevel on the mn element is mapped to CSS math-script-level]
+    expected: FAIL
+
+  [mathvariant on the mprescripts element is mapped to CSS text-transform]
+    expected: FAIL
+
+  [scriptlevel on the mo element is mapped to CSS math-script-level]
+    expected: FAIL
+
+  [scriptlevel on the annotation element is mapped to CSS math-script-level]
+    expected: FAIL
+
+  [mathvariant on the menclose element is mapped to CSS text-transform]
+    expected: FAIL
+
+  [displaystyle on the merror element is mapped to CSS math-style]
+    expected: FAIL
+
+  [displaystyle on the menclose element is mapped to CSS math-style]
+    expected: FAIL
+
+  [scriptlevel on the ms element is mapped to CSS math-script-level]
+    expected: FAIL
+
+  [scriptlevel on the mspace element is mapped to CSS math-script-level]
+    expected: FAIL
+
+  [mathvariant on the mover element is mapped to CSS text-transform]
+    expected: FAIL
+
+  [scriptlevel on the msup element is mapped to CSS math-script-level]
+    expected: FAIL
+
+  [mathvariant on the mphantom element is mapped to CSS text-transform]
+    expected: FAIL
+
+  [scriptlevel on the mover element is mapped to CSS math-script-level]
+    expected: FAIL
+
+  [mathvariant on the mi element is mapped to CSS text-transform]
+    expected: FAIL
+
+  [displaystyle on the mtext element is mapped to CSS math-style]
+    expected: FAIL
+
+  [scriptlevel on the mmultiscripts element is mapped to CSS math-script-level]
+    expected: FAIL
+
+  [mathvariant on the msubsup element is mapped to CSS text-transform]
+    expected: FAIL
+
+  [scriptlevel on the merror element is mapped to CSS math-script-level]
+    expected: FAIL
+
+  [scriptlevel on the msubsup element is mapped to CSS math-script-level]
+    expected: FAIL
+
+  [displaystyle on the munder element is mapped to CSS math-style]
+    expected: FAIL
+
+  [mathvariant on the msub element is mapped to CSS text-transform]
+    expected: FAIL
+
+  [scriptlevel on the mtd element is mapped to CSS math-script-level]
+    expected: FAIL
+
+  [mathvariant on the mtable element is mapped to CSS text-transform]
+    expected: FAIL
+
+  [mathvariant on the mfrac element is mapped to CSS text-transform]
+    expected: FAIL
+
+  [mathvariant on the none element is mapped to CSS text-transform]
+    expected: FAIL
+
+  [displaystyle on the mmultiscripts element is mapped to CSS math-style]
+    expected: FAIL
+
+  [displaystyle on the mn element is mapped to CSS math-style]
+    expected: FAIL
+
+  [displaystyle on the mi element is mapped to CSS math-style]
+    expected: FAIL
+
+  [scriptlevel on the mroot element is mapped to CSS math-script-level]
+    expected: FAIL
+
+  [scriptlevel on the mtext element is mapped to CSS math-script-level]
+    expected: FAIL
+
+  [scriptlevel on the mtr element is mapped to CSS math-script-level]
+    expected: FAIL
+
+  [scriptlevel on the mprescripts element is mapped to CSS math-script-level]
+    expected: FAIL
+
+  [displaystyle on the math element is mapped to CSS math-style]
+    expected: FAIL
+
+  [mathvariant on the mmultiscripts element is mapped to CSS text-transform]
+    expected: FAIL
+
+  [scriptlevel on the annotation-xml element is mapped to CSS math-script-level]
+    expected: FAIL
+
+  [mathvariant on the mstyle element is mapped to CSS text-transform]
+    expected: FAIL
+
+  [mathvariant on the mtext element is mapped to CSS text-transform]
+    expected: FAIL
+
+  [scriptlevel on the mphantom element is mapped to CSS math-script-level]
+    expected: FAIL
+
+  [scriptlevel on the mfrac element is mapped to CSS math-script-level]
+    expected: FAIL
+
+  [scriptlevel on the mpadded element is mapped to CSS math-script-level]
+    expected: FAIL
+
+  [displaystyle on the mfrac element is mapped to CSS math-style]
+    expected: FAIL
+
+  [displaystyle on the msubsup element is mapped to CSS math-style]
+    expected: FAIL
+
+  [displaystyle on the mrow element is mapped to CSS math-style]
+    expected: FAIL
+
+  [displaystyle on the mtable element is mapped to CSS math-style]
+    expected: FAIL
+
+  [mathvariant on the annotation-xml element is mapped to CSS text-transform]
+    expected: FAIL
+
+  [displaystyle on the none element is mapped to CSS math-style]
+    expected: FAIL
+
+  [scriptlevel on the msub element is mapped to CSS math-script-level]
+    expected: FAIL
+
+  [scriptlevel on the mrow element is mapped to CSS math-script-level]
+    expected: FAIL
+
+  [scriptlevel on the none element is mapped to CSS math-script-level]
+    expected: FAIL
+
+  [mathvariant on the mroot element is mapped to CSS text-transform]
+    expected: FAIL
+
+  [mathvariant on the math element is mapped to CSS text-transform]
+    expected: FAIL
+
+  [scriptlevel on the math element is mapped to CSS math-script-level]
+    expected: FAIL
+
+  [displaystyle on the mover element is mapped to CSS math-style]
+    expected: FAIL
+
+  [mathvariant on the mspace element is mapped to CSS text-transform]
+    expected: FAIL
+
+  [mathvariant on the msqrt element is mapped to CSS text-transform]
+    expected: FAIL
+
+  [displaystyle on the mroot element is mapped to CSS math-style]
+    expected: FAIL
+
+  [displaystyle on the mprescripts element is mapped to CSS math-style]
+    expected: FAIL
+
+  [scriptlevel on the maction element is mapped to CSS math-script-level]
+    expected: FAIL
+
+  [mathvariant on the mn element is mapped to CSS text-transform]
+    expected: FAIL
+
+  [mathvariant on the msup element is mapped to CSS text-transform]
+    expected: FAIL
+
+  [displaystyle on the mpadded element is mapped to CSS math-style]
+    expected: FAIL
+
+  [mathvariant on the ms element is mapped to CSS text-transform]
+    expected: FAIL
+
+  [displaystyle on the annotation-xml element is mapped to CSS math-style]
+    expected: FAIL
+
+  [displaystyle on the annotation element is mapped to CSS math-style]
+    expected: FAIL
+
+  [scriptlevel on the mstyle element is mapped to CSS math-script-level]
+    expected: FAIL
+
+  [scriptlevel on the mi element is mapped to CSS math-script-level]
+    expected: FAIL
+
+  [displaystyle on the semantics element is mapped to CSS math-style]
+    expected: FAIL
+
+  [mathvariant on the semantics element is mapped to CSS text-transform]
+    expected: FAIL
+
+  [scriptlevel on the semantics element is mapped to CSS math-script-level]
+    expected: FAIL
diff --git a/testing/web-platform/meta/mathml/relations/css-styling/color-001.html.ini b/testing/web-platform/meta/mathml/relations/css-styling/color-001.html.ini
new file mode 100644
index 0000000000..b8379883d9
--- /dev/null
+++ b/testing/web-platform/meta/mathml/relations/css-styling/color-001.html.ini
@@ -0,0 +1,3 @@
+[color-001.html]
+  expected:
+    if webrender and (os == "win"): FAIL
diff --git a/testing/web-platform/meta/mathml/relations/css-styling/color-002.html.ini b/testing/web-platform/meta/mathml/relations/css-styling/color-002.html.ini
new file mode 100644
index 0000000000..72307e73b2
--- /dev/null
+++ b/testing/web-platform/meta/mathml/relations/css-styling/color-002.html.ini
@@ -0,0 +1,3 @@
+[color-002.html]
+  expected:
+    if webrender and (os == "win"): FAIL
diff --git a/testing/web-platform/meta/mathml/relations/css-styling/color-003.html.ini b/testing/web-platform/meta/mathml/relations/css-styling/color-003.html.ini
new file mode 100644
index 0000000000..0788e2bf10
--- /dev/null
+++ b/testing/web-platform/meta/mathml/relations/css-styling/color-003.html.ini
@@ -0,0 +1,3 @@
+[color-003.html]
+  expected:
+    if webrender and (os == "win"): FAIL
diff --git a/testing/web-platform/meta/mathml/relations/css-styling/color-004.html.ini b/testing/web-platform/meta/mathml/relations/css-styling/color-004.html.ini
new file mode 100644
index 0000000000..9a55d53c88
--- /dev/null
+++ b/testing/web-platform/meta/mathml/relations/css-styling/color-004.html.ini
@@ -0,0 +1,5 @@
+[color-004.html]
+  expected:
+    if (os == "win") and not webrender: PASS
+    if os == "android": PASS
+    FAIL
diff --git a/testing/web-platform/meta/mathml/relations/css-styling/color-1.html.ini b/testing/web-platform/meta/mathml/relations/css-styling/color-1.html.ini
deleted file mode 100644
index 15660d84b2..0000000000
--- a/testing/web-platform/meta/mathml/relations/css-styling/color-1.html.ini
+++ /dev/null
@@ -1,5 +0,0 @@
-[color-1.html]
-  expected:
-    if (os == "linux") and not debug and webrender: "FAIL"
-    if (os == "linux") and debug and webrender: "FAIL"
-    if os == "win": "FAIL"
diff --git a/testing/web-platform/meta/mathml/relations/css-styling/lengths-1.html.ini b/testing/web-platform/meta/mathml/relations/css-styling/lengths-1.html.ini
index a6f89b54f9..283cc1343b 100644
--- a/testing/web-platform/meta/mathml/relations/css-styling/lengths-1.html.ini
+++ b/testing/web-platform/meta/mathml/relations/css-styling/lengths-1.html.ini
@@ -1,2 +1,2 @@
 [lengths-1.html]
-  expected: FAIL
+  prefs: [mathml.nonzero_unitless_lengths.disabled:true]
diff --git a/testing/web-platform/meta/mathml/relations/css-styling/lengths-2.html.ini b/testing/web-platform/meta/mathml/relations/css-styling/lengths-2.html.ini
new file mode 100644
index 0000000000..2fd5141469
--- /dev/null
+++ b/testing/web-platform/meta/mathml/relations/css-styling/lengths-2.html.ini
@@ -0,0 +1,8 @@
+[lengths-2.html]
+  prefs: [mathml.nonzero_unitless_lengths.disabled:true]
+  [Legacy namedspaces]
+    expected: FAIL
+
+  [Legacy numbers]
+    expected: FAIL
+
diff --git a/testing/web-platform/meta/mathml/relations/css-styling/mathsize-attribute-css-keywords.html.ini b/testing/web-platform/meta/mathml/relations/css-styling/mathsize-attribute-css-keywords.html.ini
new file mode 100644
index 0000000000..fb4557278c
--- /dev/null
+++ b/testing/web-platform/meta/mathml/relations/css-styling/mathsize-attribute-css-keywords.html.ini
@@ -0,0 +1,2 @@
+[mathsize-attribute-css-keywords.html]
+  prefs: [mathml.mathsize_names.disabled:true]
diff --git a/testing/web-platform/meta/mathml/relations/css-styling/mathsize-attribute-legacy-values.html.ini b/testing/web-platform/meta/mathml/relations/css-styling/mathsize-attribute-legacy-values.html.ini
new file mode 100644
index 0000000000..43edf603a9
--- /dev/null
+++ b/testing/web-platform/meta/mathml/relations/css-styling/mathsize-attribute-legacy-values.html.ini
@@ -0,0 +1,2 @@
+[mathsize-attribute-legacy-values.html]
+  prefs: [mathml.mathsize_names.disabled:true]
diff --git a/testing/web-platform/meta/mathml/relations/css-styling/padding-border-margin/border-001.html.ini b/testing/web-platform/meta/mathml/relations/css-styling/padding-border-margin/border-001.html.ini
new file mode 100644
index 0000000000..ed7dc38f23
--- /dev/null
+++ b/testing/web-platform/meta/mathml/relations/css-styling/padding-border-margin/border-001.html.ini
@@ -0,0 +1,18 @@
+[border-001.html]
+  [Border properties on mrow (logical, shorthand)]
+    expected: FAIL
+
+  [Border properties on mrow (shorthand)]
+    expected: FAIL
+
+  [Border properties on mrow (logical)]
+    expected: FAIL
+
+  [Border properties on mrow]
+    expected: FAIL
+
+  [Border properties on mrow (logical, rtl)]
+    expected: FAIL
+
+  [Border properties on mrow (rtl)]
+    expected: FAIL
diff --git a/testing/web-platform/meta/mathml/relations/css-styling/padding-border-margin/border-002.html.ini b/testing/web-platform/meta/mathml/relations/css-styling/padding-border-margin/border-002.html.ini
new file mode 100644
index 0000000000..895c1e8807
--- /dev/null
+++ b/testing/web-platform/meta/mathml/relations/css-styling/padding-border-margin/border-002.html.ini
@@ -0,0 +1,147 @@
+[border-002.html]
+  [Border properties on mspace]
+    expected: FAIL
+
+  [Border properties on mmultiscripts]
+    expected: FAIL
+
+  [Border properties on mn]
+    expected: FAIL
+
+  [Border properties on msup]
+    expected: FAIL
+
+  [Border properties on msubsup]
+    expected: FAIL
+
+  [Border properties on msub]
+    expected: FAIL
+
+  [Border properties on merror]
+    expected: FAIL
+
+  [Border properties on menclose]
+    expected: FAIL
+
+  [Border properties on msqrt]
+    expected: FAIL
+
+  [Border properties on mstyle]
+    expected: FAIL
+
+  [Border properties on maction]
+    expected: FAIL
+
+  [Border properties on munder]
+    expected: FAIL
+
+  [Border properties on mpadded]
+    expected: FAIL
+
+  [Border properties on mroot]
+    expected: FAIL
+
+  [Border properties on mi]
+    expected: FAIL
+
+  [Border properties on mphantom]
+    expected: FAIL
+
+  [Border properties on mrow]
+    expected: FAIL
+
+  [Border properties on mo]
+    expected: FAIL
+
+  [Border properties on ms]
+    expected: FAIL
+
+  [Border properties on munderover]
+    expected: FAIL
+
+  [Border properties on mtable]
+    expected: FAIL
+
+  [Border properties on semantics]
+    expected: FAIL
+
+  [Border properties on mtext]
+    expected: FAIL
+
+  [Border properties on mfrac]
+    expected: FAIL
+
+  [Border properties on mover]
+    expected: FAIL
+
+  [Border properties on msup (rtl)]
+    expected: FAIL
+
+  [Border properties on msub (rtl)]
+    expected: FAIL
+
+  [Border properties on mmultiscripts (rtl)]
+    expected: FAIL
+
+  [Border properties on mover (rtl)]
+    expected: FAIL
+
+  [Border properties on munderover (rtl)]
+    expected: FAIL
+
+  [Border properties on munder (rtl)]
+    expected: FAIL
+
+  [Border properties on msqrt (rtl)]
+    expected: FAIL
+
+  [Border properties on mrow (rtl)]
+    expected: FAIL
+
+  [Border properties on ms (rtl)]
+    expected: FAIL
+
+  [Border properties on mi (rtl)]
+    expected: FAIL
+
+  [Border properties on mfrac (rtl)]
+    expected: FAIL
+
+  [Border properties on mo (rtl)]
+    expected: FAIL
+
+  [Border properties on mroot (rtl)]
+    expected: FAIL
+
+  [Border properties on mphantom (rtl)]
+    expected: FAIL
+
+  [Border properties on maction (rtl)]
+    expected: FAIL
+
+  [Border properties on mtext (rtl)]
+    expected: FAIL
+
+  [Border properties on semantics (rtl)]
+    expected: FAIL
+
+  [Border properties on mtable (rtl)]
+    expected: FAIL
+
+  [Border properties on menclose (rtl)]
+    expected: FAIL
+
+  [Border properties on mstyle (rtl)]
+    expected: FAIL
+
+  [Border properties on msubsup (rtl)]
+    expected: FAIL
+
+  [Border properties on mpadded (rtl)]
+    expected: FAIL
+
+  [Border properties on mn (rtl)]
+    expected: FAIL
+
+  [Border properties on merror (rtl)]
+    expected: FAIL
diff --git a/testing/web-platform/meta/mathml/relations/css-styling/padding-border-margin/margin-001.html.ini b/testing/web-platform/meta/mathml/relations/css-styling/padding-border-margin/margin-001.html.ini
new file mode 100644
index 0000000000..2ebcd1d4e7
--- /dev/null
+++ b/testing/web-platform/meta/mathml/relations/css-styling/padding-border-margin/margin-001.html.ini
@@ -0,0 +1,18 @@
+[margin-001.html]
+  [Margin properties on mrow (logical, shorthand)]
+    expected: FAIL
+
+  [Margin properties on mrow (shorthand)]
+    expected: FAIL
+
+  [Margin properties on mrow (logical)]
+    expected: FAIL
+
+  [Margin properties on mrow]
+    expected: FAIL
+
+  [Margin properties on mrow (logical, rtl)]
+    expected: FAIL
+
+  [Margin properties on mrow (rtl)]
+    expected: FAIL
diff --git a/testing/web-platform/meta/mathml/relations/css-styling/padding-border-margin/margin-002.html.ini b/testing/web-platform/meta/mathml/relations/css-styling/padding-border-margin/margin-002.html.ini
new file mode 100644
index 0000000000..d9bc449359
--- /dev/null
+++ b/testing/web-platform/meta/mathml/relations/css-styling/padding-border-margin/margin-002.html.ini
@@ -0,0 +1,219 @@
+[margin-002.html]
+  [Margin properties on msup]
+    expected: FAIL
+
+  [Margin properties on msubsup]
+    expected: FAIL
+
+  [Margin properties on msub]
+    expected: FAIL
+
+  [Margin properties on merror]
+    expected: FAIL
+
+  [Margin properties on menclose]
+    expected: FAIL
+
+  [Margin properties on msqrt]
+    expected: FAIL
+
+  [Margin properties on mstyle]
+    expected: FAIL
+
+  [Margin properties on mmultiscripts]
+    expected: FAIL
+
+  [Margin properties on maction]
+    expected: FAIL
+
+  [Margin properties on munder]
+    expected: FAIL
+
+  [Margin properties on mpadded]
+    expected: FAIL
+
+  [Margin properties on mroot]
+    expected: FAIL
+
+  [Margin properties on mi]
+    expected: FAIL
+
+  [Margin properties on mphantom]
+    expected: FAIL
+
+  [Margin properties on mrow]
+    expected: FAIL
+
+  [Margin properties on mo]
+    expected: FAIL
+
+  [Margin properties on ms]
+    expected: FAIL
+
+  [Margin properties on munderover]
+    expected: FAIL
+
+  [Margin properties on mn]
+    expected: FAIL
+
+  [Margin properties on mtable]
+    expected: FAIL
+
+  [Margin properties on semantics]
+    expected: FAIL
+
+  [Margin properties on mtext]
+    expected: FAIL
+
+  [Margin properties on mfrac]
+    expected: FAIL
+
+  [Margin properties on mspace]
+    expected: FAIL
+
+  [Margin properties on mover]
+    expected: FAIL
+
+  [Margin properties on menclose (rtl)]
+    expected: FAIL
+
+  [Margin properties on mo (no margin-collapsing)]
+    expected: FAIL
+
+  [Margin properties on mi (rtl)]
+    expected: FAIL
+
+  [Margin properties on maction (no margin-collapsing)]
+    expected: FAIL
+
+  [Margin properties on msubsup (rtl)]
+    expected: FAIL
+
+  [Margin properties on mtable (no margin-collapsing)]
+    expected: FAIL
+
+  [Margin properties on msubsup (no margin-collapsing)]
+    expected: FAIL
+
+  [Margin properties on mphantom (no margin-collapsing)]
+    expected: FAIL
+
+  [Margin properties on munder (rtl)]
+    expected: FAIL
+
+  [Margin properties on mo (rtl)]
+    expected: FAIL
+
+  [Margin properties on semantics (no margin-collapsing)]
+    expected: FAIL
+
+  [Margin properties on merror (rtl)]
+    expected: FAIL
+
+  [Margin properties on mtext (rtl)]
+    expected: FAIL
+
+  [Margin properties on msqrt (no margin-collapsing)]
+    expected: FAIL
+
+  [Margin properties on mtext (no margin-collapsing)]
+    expected: FAIL
+
+  [Margin properties on mmultiscripts (rtl)]
+    expected: FAIL
+
+  [Margin properties on ms (no margin-collapsing)]
+    expected: FAIL
+
+  [Margin properties on mover (rtl)]
+    expected: FAIL
+
+  [Margin properties on msqrt (rtl)]
+    expected: FAIL
+
+  [Margin properties on menclose (no margin-collapsing)]
+    expected: FAIL
+
+  [Margin properties on mpadded (no margin-collapsing)]
+    expected: FAIL
+
+  [Margin properties on merror (no margin-collapsing)]
+    expected: FAIL
+
+  [Margin properties on msup (no margin-collapsing)]
+    expected: FAIL
+
+  [Margin properties on munderover (rtl)]
+    expected: FAIL
+
+  [Margin properties on mfrac (rtl)]
+    expected: FAIL
+
+  [Margin properties on mover (no margin-collapsing)]
+    expected: FAIL
+
+  [Margin properties on mstyle (rtl)]
+    expected: FAIL
+
+  [Margin properties on munderover (no margin-collapsing)]
+    expected: FAIL
+
+  [Margin properties on mpadded (rtl)]
+    expected: FAIL
+
+  [Margin properties on mn (rtl)]
+    expected: FAIL
+
+  [Margin properties on mmultiscripts (no margin-collapsing)]
+    expected: FAIL
+
+  [Margin properties on mrow (no margin-collapsing)]
+    expected: FAIL
+
+  [Margin properties on msub (rtl)]
+    expected: FAIL
+
+  [Margin properties on msup (rtl)]
+    expected: FAIL
+
+  [Margin properties on mroot (rtl)]
+    expected: FAIL
+
+  [Margin properties on mphantom (rtl)]
+    expected: FAIL
+
+  [Margin properties on mroot (no margin-collapsing)]
+    expected: FAIL
+
+  [Margin properties on maction (rtl)]
+    expected: FAIL
+
+  [Margin properties on mstyle (no margin-collapsing)]
+    expected: FAIL
+
+  [Margin properties on semantics (rtl)]
+    expected: FAIL
+
+  [Margin properties on mtable (rtl)]
+    expected: FAIL
+
+  [Margin properties on mn (no margin-collapsing)]
+    expected: FAIL
+
+  [Margin properties on munder (no margin-collapsing)]
+    expected: FAIL
+
+  [Margin properties on mfrac (no margin-collapsing)]
+    expected: FAIL
+
+  [Margin properties on mrow (rtl)]
+    expected: FAIL
+
+  [Margin properties on msub (no margin-collapsing)]
+    expected: FAIL
+
+  [Margin properties on ms (rtl)]
+    expected: FAIL
+
+  [Margin properties on mi (no margin-collapsing)]
+    expected: FAIL
diff --git a/testing/web-platform/meta/mathml/relations/css-styling/padding-border-margin/padding-001.html.ini b/testing/web-platform/meta/mathml/relations/css-styling/padding-border-margin/padding-001.html.ini
new file mode 100644
index 0000000000..ac818f3c82
--- /dev/null
+++ b/testing/web-platform/meta/mathml/relations/css-styling/padding-border-margin/padding-001.html.ini
@@ -0,0 +1,18 @@
+[padding-001.html]
+  [Padding properties on mrow (shorthand)]
+    expected: FAIL
+
+  [Padding properties on mrow (logical, shorthand)]
+    expected: FAIL
+
+  [Padding properties on mrow]
+    expected: FAIL
+
+  [Padding properties on mrow (logical)]
+    expected: FAIL
+
+  [Padding properties on mrow (rtl)]
+    expected: FAIL
+
+  [Padding properties on mrow (logical, rtl)]
+    expected: FAIL
diff --git a/testing/web-platform/meta/mathml/relations/css-styling/padding-border-margin/padding-002.html.ini b/testing/web-platform/meta/mathml/relations/css-styling/padding-border-margin/padding-002.html.ini
new file mode 100644
index 0000000000..c634c5805c
--- /dev/null
+++ b/testing/web-platform/meta/mathml/relations/css-styling/padding-border-margin/padding-002.html.ini
@@ -0,0 +1,147 @@
+[padding-002.html]
+  [Padding properties on mphantom]
+    expected: FAIL
+
+  [Padding properties on mspace]
+    expected: FAIL
+
+  [Padding properties on mtext]
+    expected: FAIL
+
+  [Padding properties on ms]
+    expected: FAIL
+
+  [Padding properties on msqrt]
+    expected: FAIL
+
+  [Padding properties on menclose]
+    expected: FAIL
+
+  [Padding properties on merror]
+    expected: FAIL
+
+  [Padding properties on mstyle]
+    expected: FAIL
+
+  [Padding properties on semantics]
+    expected: FAIL
+
+  [Padding properties on mn]
+    expected: FAIL
+
+  [Padding properties on mo]
+    expected: FAIL
+
+  [Padding properties on mi]
+    expected: FAIL
+
+  [Padding properties on mroot]
+    expected: FAIL
+
+  [Padding properties on munder]
+    expected: FAIL
+
+  [Padding properties on maction]
+    expected: FAIL
+
+  [Padding properties on munderover]
+    expected: FAIL
+
+  [Padding properties on msubsup]
+    expected: FAIL
+
+  [Padding properties on mtable]
+    expected: FAIL
+
+  [Padding properties on msub]
+    expected: FAIL
+
+  [Padding properties on mfrac]
+    expected: FAIL
+
+  [Padding properties on mrow]
+    expected: FAIL
+
+  [Padding properties on mmultiscripts]
+    expected: FAIL
+
+  [Padding properties on msup]
+    expected: FAIL
+
+  [Padding properties on mover]
+    expected: FAIL
+
+  [Padding properties on mpadded]
+    expected: FAIL
+
+  [Padding properties on mtext (rtl)]
+    expected: FAIL
+
+  [Padding properties on semantics (rtl)]
+    expected: FAIL
+
+  [Padding properties on munder (rtl)]
+    expected: FAIL
+
+  [Padding properties on mo (rtl)]
+    expected: FAIL
+
+  [Padding properties on mroot (rtl)]
+    expected: FAIL
+
+  [Padding properties on mn (rtl)]
+    expected: FAIL
+
+  [Padding properties on mstyle (rtl)]
+    expected: FAIL
+
+  [Padding properties on merror (rtl)]
+    expected: FAIL
+
+  [Padding properties on msub (rtl)]
+    expected: FAIL
+
+  [Padding properties on mmultiscripts (rtl)]
+    expected: FAIL
+
+  [Padding properties on menclose (rtl)]
+    expected: FAIL
+
+  [Padding properties on msubsup (rtl)]
+    expected: FAIL
+
+  [Padding properties on msup (rtl)]
+    expected: FAIL
+
+  [Padding properties on mover (rtl)]
+    expected: FAIL
+
+  [Padding properties on mpadded (rtl)]
+    expected: FAIL
+
+  [Padding properties on mi (rtl)]
+    expected: FAIL
+
+  [Padding properties on maction (rtl)]
+    expected: FAIL
+
+  [Padding properties on ms (rtl)]
+    expected: FAIL
+
+  [Padding properties on mrow (rtl)]
+    expected: FAIL
+
+  [Padding properties on mphantom (rtl)]
+    expected: FAIL
+
+  [Padding properties on mtable (rtl)]
+    expected: FAIL
+
+  [Padding properties on mfrac (rtl)]
+    expected: FAIL
+
+  [Padding properties on msqrt (rtl)]
+    expected: FAIL
+
+  [Padding properties on munderover (rtl)]
+    expected: FAIL
diff --git a/testing/web-platform/meta/mathml/relations/css-styling/width-height-001.html.ini b/testing/web-platform/meta/mathml/relations/css-styling/width-height-001.html.ini
new file mode 100644
index 0000000000..14c7972119
--- /dev/null
+++ b/testing/web-platform/meta/mathml/relations/css-styling/width-height-001.html.ini
@@ -0,0 +1,6 @@
+[width-height-001.html]
+  [inline-size and block-size properties on merror]
+    expected: FAIL
+
+  [width and height properties on merror]
+    expected: FAIL
diff --git a/testing/web-platform/meta/mathml/relations/css-styling/writing-mode/writing-mode-001.html.ini b/testing/web-platform/meta/mathml/relations/css-styling/writing-mode/writing-mode-001.html.ini
new file mode 100644
index 0000000000..c670d8ea4d
--- /dev/null
+++ b/testing/web-platform/meta/mathml/relations/css-styling/writing-mode/writing-mode-001.html.ini
@@ -0,0 +1,19 @@
+[writing-mode-001.html]
+  [Inheritance of CSS writing-mode and direction (id='vertical-rl_ltr')]
+    expected: FAIL
+
+  [Layout of mrow (id='vertical-lr_ltr')]
+    expected: FAIL
+
+  [Inheritance of CSS writing-mode and direction (id='vertical-lr_ltr')]
+    expected: FAIL
+
+  [Inheritance of CSS writing-mode and direction (id='vertical-lr_rtl')]
+    expected: FAIL
+
+  [Inheritance of CSS writing-mode and direction (id='vertical-rl_rtl')]
+    expected: FAIL
+
+  [Layout of mrow (id='vertical-rl_ltr')]
+    expected: FAIL
+
diff --git a/testing/web-platform/meta/mathml/relations/css-styling/writing-mode/writing-mode-002.html.ini b/testing/web-platform/meta/mathml/relations/css-styling/writing-mode/writing-mode-002.html.ini
new file mode 100644
index 0000000000..5681d7897f
--- /dev/null
+++ b/testing/web-platform/meta/mathml/relations/css-styling/writing-mode/writing-mode-002.html.ini
@@ -0,0 +1,372 @@
+[writing-mode-002.html]
+  [Layout of mmultiscripts (writing-mode: vertical-rl; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of merror (writing-mode: vertical-rl; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of msubsup (writing-mode: vertical-rl; direction: ltr;)]
+    expected: FAIL
+
+  [Layout of merror (writing-mode: vertical-lr; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of mroot (writing-mode: vertical-rl; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of munder (writing-mode: vertical-lr; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of mover (writing-mode: vertical-lr; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of mspace (writing-mode: vertical-rl; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of msup (writing-mode: vertical-lr; direction: ltr;)]
+    expected: FAIL
+
+  [Layout of mo (writing-mode: vertical-lr; direction: ltr;)]
+    expected: FAIL
+
+  [Layout of msup (writing-mode: vertical-lr; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of mi (writing-mode: vertical-lr; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of none (writing-mode: vertical-rl; direction: ltr;)]
+    expected: FAIL
+
+  [Layout of semantics (writing-mode: vertical-rl; direction: ltr;)]
+    expected: FAIL
+
+  [Layout of mtext (writing-mode: vertical-rl; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of mrow (writing-mode: vertical-lr; direction: ltr;)]
+    expected: FAIL
+
+  [Layout of ms (writing-mode: vertical-rl; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of mn (writing-mode: horizontal-tb; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of msqrt (writing-mode: vertical-rl; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of munderover (writing-mode: vertical-rl; direction: ltr;)]
+    expected: FAIL
+
+  [Layout of mpadded (writing-mode: vertical-rl; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of merror (writing-mode: vertical-rl; direction: ltr;)]
+    expected: FAIL
+
+  [Layout of mrow (writing-mode: vertical-rl; direction: ltr;)]
+    expected: FAIL
+
+  [Layout of ms (writing-mode: horizontal-tb; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of mo (writing-mode: horizontal-tb; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of mtext (writing-mode: vertical-lr; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of mtd (writing-mode: vertical-lr; direction: ltr;)]
+    expected: FAIL
+
+  [Layout of mrow (writing-mode: vertical-rl; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of maction (writing-mode: vertical-rl; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of mn (writing-mode: vertical-lr; direction: ltr;)]
+    expected: FAIL
+
+  [Layout of munderover (writing-mode: vertical-lr; direction: ltr;)]
+    expected: FAIL
+
+  [Layout of msubsup (writing-mode: vertical-lr; direction: ltr;)]
+    expected: FAIL
+
+  [Layout of mtd (writing-mode: vertical-rl; direction: ltr;)]
+    expected: FAIL
+
+  [Layout of mi (writing-mode: horizontal-tb; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of mi (writing-mode: vertical-rl; direction: ltr;)]
+    expected: FAIL
+
+  [Layout of msub (writing-mode: vertical-lr; direction: ltr;)]
+    expected: FAIL
+
+  [Layout of mstyle (writing-mode: vertical-rl; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of mover (writing-mode: vertical-rl; direction: ltr;)]
+    expected: FAIL
+
+  [Layout of ms (writing-mode: vertical-lr; direction: ltr;)]
+    expected: FAIL
+
+  [Layout of menclose (writing-mode: horizontal-tb; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of mspace (writing-mode: vertical-lr; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of mfrac (writing-mode: vertical-lr; direction: ltr;)]
+    expected: FAIL
+
+  [Layout of mo (writing-mode: vertical-lr; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of mphantom (writing-mode: vertical-lr; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of ms (writing-mode: vertical-rl; direction: ltr;)]
+    expected: FAIL
+
+  [Layout of msqrt (writing-mode: vertical-lr; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of maction (writing-mode: vertical-lr; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of mroot (writing-mode: vertical-lr; direction: ltr;)]
+    expected: FAIL
+
+  [Layout of semantics (writing-mode: horizontal-tb; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of maction (writing-mode: vertical-rl; direction: ltr;)]
+    expected: FAIL
+
+  [Layout of msub (writing-mode: vertical-lr; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of mstyle (writing-mode: vertical-rl; direction: ltr;)]
+    expected: FAIL
+
+  [Layout of mover (writing-mode: vertical-rl; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of msqrt (writing-mode: vertical-lr; direction: ltr;)]
+    expected: FAIL
+
+  [Layout of mtext (writing-mode: horizontal-tb; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of mmultiscripts (writing-mode: vertical-lr; direction: ltr;)]
+    expected: FAIL
+
+  [Layout of mtr (writing-mode: vertical-rl; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of munder (writing-mode: vertical-rl; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of none (writing-mode: vertical-rl; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of none (writing-mode: vertical-lr; direction: ltr;)]
+    expected: FAIL
+
+  [Layout of semantics (writing-mode: vertical-lr; direction: ltr;)]
+    expected: FAIL
+
+  [Layout of mstyle (writing-mode: vertical-lr; direction: ltr;)]
+    expected: FAIL
+
+  [Layout of mmultiscripts (writing-mode: vertical-lr; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of mtable (writing-mode: vertical-lr; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of mstyle (writing-mode: vertical-lr; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of menclose (writing-mode: vertical-rl; direction: ltr;)]
+    expected: FAIL
+
+  [Layout of mtext (writing-mode: vertical-lr; direction: ltr;)]
+    expected: FAIL
+
+  [Layout of mtd (writing-mode: vertical-lr; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of mpadded (writing-mode: vertical-lr; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of merror (writing-mode: vertical-lr; direction: ltr;)]
+    expected: FAIL
+
+  [Layout of mroot (writing-mode: vertical-rl; direction: ltr;)]
+    expected: FAIL
+
+  [Layout of mtr (writing-mode: vertical-lr; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of munder (writing-mode: vertical-rl; direction: ltr;)]
+    expected: FAIL
+
+  [Layout of mprescripts (writing-mode: vertical-rl; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of mspace (writing-mode: vertical-rl; direction: ltr;)]
+    expected: FAIL
+
+  [Layout of mfrac (writing-mode: vertical-rl; direction: ltr;)]
+    expected: FAIL
+
+  [Layout of mi (writing-mode: vertical-rl; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of mi (writing-mode: vertical-lr; direction: ltr;)]
+    expected: FAIL
+
+  [Layout of semantics (writing-mode: vertical-rl; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of mpadded (writing-mode: vertical-lr; direction: ltr;)]
+    expected: FAIL
+
+  [Layout of mtable (writing-mode: vertical-lr; direction: ltr;)]
+    expected: FAIL
+
+  [Layout of mrow (writing-mode: vertical-lr; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of munderover (writing-mode: vertical-rl; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of maction (writing-mode: horizontal-tb; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of menclose (writing-mode: vertical-rl; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of mpadded (writing-mode: vertical-rl; direction: ltr;)]
+    expected: FAIL
+
+  [Layout of mn (writing-mode: vertical-lr; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of mover (writing-mode: vertical-lr; direction: ltr;)]
+    expected: FAIL
+
+  [Layout of msub (writing-mode: vertical-rl; direction: ltr;)]
+    expected: FAIL
+
+  [Layout of munderover (writing-mode: vertical-lr; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of mphantom (writing-mode: vertical-rl; direction: ltr;)]
+    expected: FAIL
+
+  [Layout of mprescripts (writing-mode: vertical-lr; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of mo (writing-mode: vertical-rl; direction: ltr;)]
+    expected: FAIL
+
+  [Layout of mtable (writing-mode: vertical-rl; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of mphantom (writing-mode: vertical-rl; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of msubsup (writing-mode: vertical-lr; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of mtd (writing-mode: vertical-rl; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of mo (writing-mode: vertical-rl; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of mn (writing-mode: vertical-rl; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of mmultiscripts (writing-mode: vertical-rl; direction: ltr;)]
+    expected: FAIL
+
+  [Layout of mtr (writing-mode: vertical-rl; direction: ltr;)]
+    expected: FAIL
+
+  [Layout of munder (writing-mode: vertical-lr; direction: ltr;)]
+    expected: FAIL
+
+  [Layout of mspace (writing-mode: vertical-lr; direction: ltr;)]
+    expected: FAIL
+
+  [Layout of msup (writing-mode: vertical-rl; direction: ltr;)]
+    expected: FAIL
+
+  [Layout of mfrac (writing-mode: vertical-lr; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of mphantom (writing-mode: vertical-lr; direction: ltr;)]
+    expected: FAIL
+
+  [Layout of menclose (writing-mode: vertical-lr; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of mtable (writing-mode: vertical-rl; direction: ltr;)]
+    expected: FAIL
+
+  [Layout of msub (writing-mode: vertical-rl; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of mprescripts (writing-mode: vertical-rl; direction: ltr;)]
+    expected: FAIL
+
+  [Layout of mprescripts (writing-mode: vertical-lr; direction: ltr;)]
+    expected: FAIL
+
+  [Layout of maction (writing-mode: vertical-lr; direction: ltr;)]
+    expected: FAIL
+
+  [Layout of mroot (writing-mode: vertical-lr; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of mtext (writing-mode: vertical-rl; direction: ltr;)]
+    expected: FAIL
+
+  [Layout of ms (writing-mode: vertical-lr; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of mtr (writing-mode: vertical-lr; direction: ltr;)]
+    expected: FAIL
+
+  [Layout of msqrt (writing-mode: vertical-rl; direction: ltr;)]
+    expected: FAIL
+
+  [Layout of msup (writing-mode: vertical-rl; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of mn (writing-mode: vertical-rl; direction: ltr;)]
+    expected: FAIL
+
+  [Layout of mfrac (writing-mode: vertical-rl; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of msubsup (writing-mode: vertical-rl; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of menclose (writing-mode: vertical-lr; direction: ltr;)]
+    expected: FAIL
+
+  [Layout of none (writing-mode: vertical-lr; direction: rtl;)]
+    expected: FAIL
+
+  [Layout of semantics (writing-mode: vertical-lr; direction: rtl;)]
+    expected: FAIL
diff --git a/testing/web-platform/meta/paint-timing/__dir__.ini b/testing/web-platform/meta/paint-timing/__dir__.ini
deleted file mode 100644
index e69de29bb2..0000000000
diff --git a/testing/web-platform/meta/paint-timing/fcp-only/fcp-background-size.html.ini b/testing/web-platform/meta/paint-timing/fcp-only/fcp-background-size.html.ini
deleted file mode 100644
index 6fd58633f9..0000000000
--- a/testing/web-platform/meta/paint-timing/fcp-only/fcp-background-size.html.ini
+++ /dev/null
@@ -1,4 +0,0 @@
-[fcp-background-size.html]
-  [First contentful paint fires due to background size.]
-    expected: FAIL
-
diff --git a/testing/web-platform/meta/paint-timing/fcp-only/fcp-bg-image-set.html.ini b/testing/web-platform/meta/paint-timing/fcp-only/fcp-bg-image-set.html.ini
index f874030d6f..83b34d38dc 100644
--- a/testing/web-platform/meta/paint-timing/fcp-only/fcp-bg-image-set.html.ini
+++ b/testing/web-platform/meta/paint-timing/fcp-only/fcp-bg-image-set.html.ini
@@ -1,4 +1,5 @@
 [fcp-bg-image-set.html]
+  expected: TIMEOUT
   [First contentful paint fires due to background image in image-set.]
-    expected: FAIL
+    expected: TIMEOUT # We don't have image-set supported yet
 
diff --git a/testing/web-platform/meta/paint-timing/fcp-only/fcp-bg-image-two-steps.html.ini b/testing/web-platform/meta/paint-timing/fcp-only/fcp-bg-image-two-steps.html.ini
deleted file mode 100644
index b1537e0f1a..0000000000
--- a/testing/web-platform/meta/paint-timing/fcp-only/fcp-bg-image-two-steps.html.ini
+++ /dev/null
@@ -1,4 +0,0 @@
-[fcp-bg-image-two-steps.html]
-  [First contentful paint fires for background image only when visible.]
-    expected: FAIL
-
diff --git a/testing/web-platform/meta/paint-timing/fcp-only/fcp-canvas-context.html.ini b/testing/web-platform/meta/paint-timing/fcp-only/fcp-canvas-context.html.ini
deleted file mode 100644
index 6b79abdf32..0000000000
--- a/testing/web-platform/meta/paint-timing/fcp-only/fcp-canvas-context.html.ini
+++ /dev/null
@@ -1,4 +0,0 @@
-[fcp-canvas-context.html]
-  [Canvas should count as contentful when context is created]
-    expected: FAIL
-
diff --git a/testing/web-platform/meta/paint-timing/fcp-only/fcp-gradient.html.ini b/testing/web-platform/meta/paint-timing/fcp-only/fcp-gradient.html.ini
deleted file mode 100644
index 7f0ad51c38..0000000000
--- a/testing/web-platform/meta/paint-timing/fcp-only/fcp-gradient.html.ini
+++ /dev/null
@@ -1,4 +0,0 @@
-[fcp-gradient.html]
-  [Gradients should not count as contentful]
-    expected: FAIL
-
diff --git a/testing/web-platform/meta/paint-timing/fcp-only/fcp-invisible-3d-rotate-descendant.html.ini b/testing/web-platform/meta/paint-timing/fcp-only/fcp-invisible-3d-rotate-descendant.html.ini
deleted file mode 100644
index 562e0cadf7..0000000000
--- a/testing/web-platform/meta/paint-timing/fcp-only/fcp-invisible-3d-rotate-descendant.html.ini
+++ /dev/null
@@ -1,4 +0,0 @@
-[fcp-invisible-3d-rotate-descendant.html]
-  [First contentful paint fires due to its ancestor getting rotating into view.]
-    expected: FAIL
-
diff --git a/testing/web-platform/meta/paint-timing/fcp-only/fcp-invisible-3d-rotate.html.ini b/testing/web-platform/meta/paint-timing/fcp-only/fcp-invisible-3d-rotate.html.ini
deleted file mode 100644
index f67b0f055c..0000000000
--- a/testing/web-platform/meta/paint-timing/fcp-only/fcp-invisible-3d-rotate.html.ini
+++ /dev/null
@@ -1,4 +0,0 @@
-[fcp-invisible-3d-rotate.html]
-  [First contentful paint fires due to 3d rotation into view.]
-    expected: FAIL
-
diff --git a/testing/web-platform/meta/paint-timing/fcp-only/fcp-invisible-scale-transition.html.ini b/testing/web-platform/meta/paint-timing/fcp-only/fcp-invisible-scale-transition.html.ini
deleted file mode 100644
index cdff37c849..0000000000
--- a/testing/web-platform/meta/paint-timing/fcp-only/fcp-invisible-scale-transition.html.ini
+++ /dev/null
@@ -1,4 +0,0 @@
-[fcp-invisible-scale-transition.html]
-  [First contentful paint fires when revealed during transition.]
-    expected: FAIL
-
diff --git a/testing/web-platform/meta/paint-timing/fcp-only/fcp-invisible-scale.html.ini b/testing/web-platform/meta/paint-timing/fcp-only/fcp-invisible-scale.html.ini
deleted file mode 100644
index 576cf15c11..0000000000
--- a/testing/web-platform/meta/paint-timing/fcp-only/fcp-invisible-scale.html.ini
+++ /dev/null
@@ -1,4 +0,0 @@
-[fcp-invisible-scale.html]
-  [First contentful paint fires due to scale becoming positive.]
-    expected: FAIL
-
diff --git a/testing/web-platform/meta/paint-timing/fcp-only/fcp-invisible-text.html.ini b/testing/web-platform/meta/paint-timing/fcp-only/fcp-invisible-text.html.ini
deleted file mode 100644
index 372c118655..0000000000
--- a/testing/web-platform/meta/paint-timing/fcp-only/fcp-invisible-text.html.ini
+++ /dev/null
@@ -1,4 +0,0 @@
-[fcp-invisible-text.html]
-  [First contentful paint fires due to pseudo-element becoming visible.]
-    expected: FAIL
-
diff --git a/testing/web-platform/meta/paint-timing/fcp-only/fcp-opacity-descendant.html.ini b/testing/web-platform/meta/paint-timing/fcp-only/fcp-opacity-descendant.html.ini
deleted file mode 100644
index a9340e5ab0..0000000000
--- a/testing/web-platform/meta/paint-timing/fcp-only/fcp-opacity-descendant.html.ini
+++ /dev/null
@@ -1,4 +0,0 @@
-[fcp-opacity-descendant.html]
-  [First contentful paint fires due to its ancestor getting positive opacity.]
-    expected: FAIL
-
diff --git a/testing/web-platform/meta/paint-timing/fcp-only/fcp-opacity.html.ini b/testing/web-platform/meta/paint-timing/fcp-only/fcp-opacity.html.ini
deleted file mode 100644
index 5f637310f5..0000000000
--- a/testing/web-platform/meta/paint-timing/fcp-only/fcp-opacity.html.ini
+++ /dev/null
@@ -1,4 +0,0 @@
-[fcp-opacity.html]
-  [First contentful paint fires due to opacity-revealed element.]
-    expected: FAIL
-
diff --git a/testing/web-platform/meta/paint-timing/fcp-only/fcp-out-of-bounds-translate.html.ini b/testing/web-platform/meta/paint-timing/fcp-only/fcp-out-of-bounds-translate.html.ini
deleted file mode 100644
index 4c1ff907b6..0000000000
--- a/testing/web-platform/meta/paint-timing/fcp-only/fcp-out-of-bounds-translate.html.ini
+++ /dev/null
@@ -1,4 +0,0 @@
-[fcp-out-of-bounds-translate.html]
-  [First contentful paint fires due to transform-based intersection with document.]
-    expected: FAIL
-
diff --git a/testing/web-platform/meta/paint-timing/fcp-only/fcp-out-of-bounds.html.ini b/testing/web-platform/meta/paint-timing/fcp-only/fcp-out-of-bounds.html.ini
deleted file mode 100644
index 2155df5b33..0000000000
--- a/testing/web-platform/meta/paint-timing/fcp-only/fcp-out-of-bounds.html.ini
+++ /dev/null
@@ -1,4 +0,0 @@
-[fcp-out-of-bounds.html]
-  [First contentful paint fires due to intersection with document.]
-    expected: FAIL
-
diff --git a/testing/web-platform/meta/paint-timing/fcp-only/fcp-pseudo-element-display.html.ini b/testing/web-platform/meta/paint-timing/fcp-only/fcp-pseudo-element-display.html.ini
deleted file mode 100644
index 2e4d1c44fa..0000000000
--- a/testing/web-platform/meta/paint-timing/fcp-only/fcp-pseudo-element-display.html.ini
+++ /dev/null
@@ -1,4 +0,0 @@
-[fcp-pseudo-element-display.html]
-  [First contentful paint fires due to pseudo-element text.]
-    expected: FAIL
-
diff --git a/testing/web-platform/meta/paint-timing/fcp-only/fcp-pseudo-element-image.html.ini b/testing/web-platform/meta/paint-timing/fcp-only/fcp-pseudo-element-image.html.ini
deleted file mode 100644
index 49076e02d6..0000000000
--- a/testing/web-platform/meta/paint-timing/fcp-only/fcp-pseudo-element-image.html.ini
+++ /dev/null
@@ -1,4 +0,0 @@
-[fcp-pseudo-element-image.html]
-  [First contentful paint fires due to pseudo-element image.]
-    expected: FAIL
-
diff --git a/testing/web-platform/meta/paint-timing/fcp-only/fcp-pseudo-element-opacity.html.ini b/testing/web-platform/meta/paint-timing/fcp-only/fcp-pseudo-element-opacity.html.ini
deleted file mode 100644
index fb58ad53cc..0000000000
--- a/testing/web-platform/meta/paint-timing/fcp-only/fcp-pseudo-element-opacity.html.ini
+++ /dev/null
@@ -1,4 +0,0 @@
-[fcp-pseudo-element-opacity.html]
-  [First contentful paint fires due to pseudo-element getting positive opacity.]
-    expected: FAIL
-
diff --git a/testing/web-platform/meta/paint-timing/fcp-only/fcp-pseudo-element-text.html.ini b/testing/web-platform/meta/paint-timing/fcp-only/fcp-pseudo-element-text.html.ini
deleted file mode 100644
index ac5dedd902..0000000000
--- a/testing/web-platform/meta/paint-timing/fcp-only/fcp-pseudo-element-text.html.ini
+++ /dev/null
@@ -1,4 +0,0 @@
-[fcp-pseudo-element-text.html]
-  [First contentful paint fires due to pseudo-element text.]
-    expected: FAIL
-
diff --git a/testing/web-platform/meta/paint-timing/fcp-only/fcp-pseudo-element-visibility.html.ini b/testing/web-platform/meta/paint-timing/fcp-only/fcp-pseudo-element-visibility.html.ini
deleted file mode 100644
index f4afd3c99d..0000000000
--- a/testing/web-platform/meta/paint-timing/fcp-only/fcp-pseudo-element-visibility.html.ini
+++ /dev/null
@@ -1,4 +0,0 @@
-[fcp-pseudo-element-visibility.html]
-  [First contentful paint fires due to pseudo-element becoming visible.]
-    expected: FAIL
-
diff --git a/testing/web-platform/meta/paint-timing/fcp-only/fcp-svg.html.ini b/testing/web-platform/meta/paint-timing/fcp-only/fcp-svg.html.ini
deleted file mode 100644
index 032c8b8ef0..0000000000
--- a/testing/web-platform/meta/paint-timing/fcp-only/fcp-svg.html.ini
+++ /dev/null
@@ -1,4 +0,0 @@
-[fcp-svg.html]
-  [First contentful paint fires when SVG becomes contentful.]
-    expected: FAIL
-
diff --git a/testing/web-platform/meta/paint-timing/fcp-only/fcp-text-input.html.ini b/testing/web-platform/meta/paint-timing/fcp-only/fcp-text-input.html.ini
new file mode 100644
index 0000000000..b035194dca
--- /dev/null
+++ b/testing/web-platform/meta/paint-timing/fcp-only/fcp-text-input.html.ini
@@ -0,0 +1,4 @@
+[fcp-text-input.html]
+  [Text input should become contentful when its value is non-empty]
+    expected: FAIL
+
diff --git a/testing/web-platform/meta/paint-timing/fcp-only/fcp-video-frame.html.ini b/testing/web-platform/meta/paint-timing/fcp-only/fcp-video-frame.html.ini
index 9b753533f5..fbf2c5ee45 100644
--- a/testing/web-platform/meta/paint-timing/fcp-only/fcp-video-frame.html.ini
+++ b/testing/web-platform/meta/paint-timing/fcp-only/fcp-video-frame.html.ini
@@ -1,4 +1,5 @@
 [fcp-video-frame.html]
+  expected: TIMEOUT
   [Video should become contentful when first frame is loaded]
-    expected: FAIL
+    expected: TIMEOUT # Bug 1652605
 
diff --git a/testing/web-platform/meta/paint-timing/fcp-only/fcp-video-poster.html.ini b/testing/web-platform/meta/paint-timing/fcp-only/fcp-video-poster.html.ini
deleted file mode 100644
index a5233fb94b..0000000000
--- a/testing/web-platform/meta/paint-timing/fcp-only/fcp-video-poster.html.ini
+++ /dev/null
@@ -1,4 +0,0 @@
-[fcp-video-poster.html]
-  [Video should become contentful when poster is loaded]
-    expected: FAIL
-
diff --git a/testing/web-platform/meta/paint-timing/fcp-only/fcp-whitespace.html.ini b/testing/web-platform/meta/paint-timing/fcp-only/fcp-whitespace.html.ini
deleted file mode 100644
index ca5669692f..0000000000
--- a/testing/web-platform/meta/paint-timing/fcp-only/fcp-whitespace.html.ini
+++ /dev/null
@@ -1,4 +0,0 @@
-[fcp-whitespace.html]
-  [Whitespace should not count as contentful.]
-    expected: FAIL
-
diff --git a/testing/web-platform/meta/paint-timing/first-contentful-canvas-none.html.ini b/testing/web-platform/meta/paint-timing/first-contentful-canvas-none.html.ini
new file mode 100644
index 0000000000..79957ffafa
--- /dev/null
+++ b/testing/web-platform/meta/paint-timing/first-contentful-canvas-none.html.ini
@@ -0,0 +1,3 @@
+[first-contentful-canvas-none.html]
+  [First contentful paint should not fire for canvas type none]
+    expected: FAIL
diff --git a/testing/web-platform/meta/paint-timing/idlharness.window.js.ini b/testing/web-platform/meta/paint-timing/idlharness.window.js.ini
deleted file mode 100644
index 99dd19b81a..0000000000
--- a/testing/web-platform/meta/paint-timing/idlharness.window.js.ini
+++ /dev/null
@@ -1,31 +0,0 @@
-[idlharness.window.html]
-  [PerformancePaintTiming interface: existence and properties of interface object]
-    expected: FAIL
-
-  [PerformancePaintTiming interface object length]
-    expected: FAIL
-
-  [PerformancePaintTiming interface object name]
-    expected: FAIL
-
-  [PerformancePaintTiming interface: existence and properties of interface prototype object]
-    expected: FAIL
-
-  [PerformancePaintTiming interface: existence and properties of interface prototype object's "constructor" property]
-    expected: FAIL
-
-  [PerformancePaintTiming interface: existence and properties of interface prototype object's @@unscopables property]
-    expected: FAIL
-
-  [PerformancePaintTiming must be primary interface of paintTiming]
-    expected: FAIL
-
-  [Stringification of paintTiming]
-    expected: FAIL
-
-  [paint-timing interfaces.]
-    expected: FAIL
-
-  [idl_test setup]
-    expected: FAIL
-
diff --git a/testing/web-platform/meta/paint-timing/input-text.html.ini b/testing/web-platform/meta/paint-timing/input-text.html.ini
deleted file mode 100644
index dd4eba3459..0000000000
--- a/testing/web-platform/meta/paint-timing/input-text.html.ini
+++ /dev/null
@@ -1,4 +0,0 @@
-[input-text.html]
-  [Text from a form control triggers First Contentful Paint.]
-    expected: FAIL
-
diff --git a/testing/web-platform/meta/paint-timing/replaced-content-image.html.ini b/testing/web-platform/meta/paint-timing/replaced-content-image.html.ini
index 9c22c20336..4643cda658 100644
--- a/testing/web-platform/meta/paint-timing/replaced-content-image.html.ini
+++ b/testing/web-platform/meta/paint-timing/replaced-content-image.html.ini
@@ -1,3 +1,5 @@
 [replaced-content-image.html]
+  expected: TIMEOUT
   [Replaced content image triggers First Contentful Paint.]
-    expected: FAIL
+    expected: TIMEOUT
+
diff --git a/testing/web-platform/meta/paint-timing/supported-paint-type.window.js.ini b/testing/web-platform/meta/paint-timing/supported-paint-type.window.js.ini
deleted file mode 100644
index a36fcf8b42..0000000000
--- a/testing/web-platform/meta/paint-timing/supported-paint-type.window.js.ini
+++ /dev/null
@@ -1,4 +0,0 @@
-[supported-paint-type.window.html]
-  [supportedEntryTypes contains 'paint'.]
-    expected: FAIL
-
diff --git a/testing/web-platform/meta/paint-timing/basetest.html.ini b/testing/web-platform/meta/paint-timing/with-first-paint/basetest.html.ini
similarity index 57%
rename from testing/web-platform/meta/paint-timing/basetest.html.ini
rename to testing/web-platform/meta/paint-timing/with-first-paint/basetest.html.ini
index b1eef6e38b..22ef06a2ad 100644
--- a/testing/web-platform/meta/paint-timing/basetest.html.ini
+++ b/testing/web-platform/meta/paint-timing/with-first-paint/basetest.html.ini
@@ -1,5 +1,5 @@
 [basetest.html]
   expected: TIMEOUT
   [Basic test to check existence of FP and FCP.]
-    expected: TIMEOUT
+    expected: TIMEOUT # Expect timeout because we don't have FP
 
diff --git a/testing/web-platform/meta/paint-timing/border-image.html.ini b/testing/web-platform/meta/paint-timing/with-first-paint/border-image.html.ini
similarity index 61%
rename from testing/web-platform/meta/paint-timing/border-image.html.ini
rename to testing/web-platform/meta/paint-timing/with-first-paint/border-image.html.ini
index a10405e8c2..0288fbfb8b 100644
--- a/testing/web-platform/meta/paint-timing/border-image.html.ini
+++ b/testing/web-platform/meta/paint-timing/with-first-paint/border-image.html.ini
@@ -1,3 +1,5 @@
 [border-image.html]
+  expected: TIMEOUT
   [Border image triggers First Contentful Paint.]
-    expected: FAIL
+    expected: TIMEOUT
+
diff --git a/testing/web-platform/meta/paint-timing/with-first-paint/buffered-flag.window.js.ini b/testing/web-platform/meta/paint-timing/with-first-paint/buffered-flag.window.js.ini
new file mode 100644
index 0000000000..fe779d9946
--- /dev/null
+++ b/testing/web-platform/meta/paint-timing/with-first-paint/buffered-flag.window.js.ini
@@ -0,0 +1,5 @@
+[buffered-flag.window.html]
+  expected: TIMEOUT
+  [PerformanceObserver with buffered flag sees previous paint entries.]
+    expected: TIMEOUT # Expect timeout because we don't have FP
+
diff --git a/testing/web-platform/meta/paint-timing/child-painting-first-image.html.ini b/testing/web-platform/meta/paint-timing/with-first-paint/child-painting-first-image.html.ini
similarity index 67%
rename from testing/web-platform/meta/paint-timing/child-painting-first-image.html.ini
rename to testing/web-platform/meta/paint-timing/with-first-paint/child-painting-first-image.html.ini
index bc4357ecaa..5cdf272917 100644
--- a/testing/web-platform/meta/paint-timing/child-painting-first-image.html.ini
+++ b/testing/web-platform/meta/paint-timing/with-first-paint/child-painting-first-image.html.ini
@@ -1,5 +1,5 @@
 [child-painting-first-image.html]
   expected: TIMEOUT
   [Parent frame ignores paint-timing events fired from child image rendering.]
-    expected: TIMEOUT
+    expected: TIMEOUT # Expect timeout because we don't have FP
 
diff --git a/testing/web-platform/meta/paint-timing/first-contentful-bg-image.html.ini b/testing/web-platform/meta/paint-timing/with-first-paint/first-contentful-bg-image.html.ini
similarity index 65%
rename from testing/web-platform/meta/paint-timing/first-contentful-bg-image.html.ini
rename to testing/web-platform/meta/paint-timing/with-first-paint/first-contentful-bg-image.html.ini
index 46e5160e0d..2b9a52481d 100644
--- a/testing/web-platform/meta/paint-timing/first-contentful-bg-image.html.ini
+++ b/testing/web-platform/meta/paint-timing/with-first-paint/first-contentful-bg-image.html.ini
@@ -1,5 +1,5 @@
 [first-contentful-bg-image.html]
   expected: TIMEOUT
   [First contentful paint fires due to background image render.]
-    expected: TIMEOUT
+    expected: TIMEOUT # Expect timeout because we don't have FP
 
diff --git a/testing/web-platform/meta/paint-timing/with-first-paint/first-contentful-canvas-webgl2.html.ini b/testing/web-platform/meta/paint-timing/with-first-paint/first-contentful-canvas-webgl2.html.ini
new file mode 100644
index 0000000000..7e83019e6a
--- /dev/null
+++ b/testing/web-platform/meta/paint-timing/with-first-paint/first-contentful-canvas-webgl2.html.ini
@@ -0,0 +1,3 @@
+[first-contentful-canvas-webgl2.html]
+  [First contentful paint fires due to webgl2 canvas render.]
+    expected: FAIL
diff --git a/testing/web-platform/meta/paint-timing/first-contentful-canvas.html.ini b/testing/web-platform/meta/paint-timing/with-first-paint/first-contentful-canvas.html.ini
similarity index 62%
rename from testing/web-platform/meta/paint-timing/first-contentful-canvas.html.ini
rename to testing/web-platform/meta/paint-timing/with-first-paint/first-contentful-canvas.html.ini
index 95e85ca4ae..840baa00dd 100644
--- a/testing/web-platform/meta/paint-timing/first-contentful-canvas.html.ini
+++ b/testing/web-platform/meta/paint-timing/with-first-paint/first-contentful-canvas.html.ini
@@ -1,5 +1,5 @@
 [first-contentful-canvas.html]
   expected: TIMEOUT
   [First contentful paint fires due to canvas render.]
-    expected: TIMEOUT
+    expected: TIMEOUT # Expect timeout because we don't have FP
 
diff --git a/testing/web-platform/meta/paint-timing/first-contentful-image.html.ini b/testing/web-platform/meta/paint-timing/with-first-paint/first-contentful-image.html.ini
similarity index 57%
rename from testing/web-platform/meta/paint-timing/first-contentful-image.html.ini
rename to testing/web-platform/meta/paint-timing/with-first-paint/first-contentful-image.html.ini
index a8c836bfe8..b7895027b4 100644
--- a/testing/web-platform/meta/paint-timing/first-contentful-image.html.ini
+++ b/testing/web-platform/meta/paint-timing/with-first-paint/first-contentful-image.html.ini
@@ -1,5 +1,4 @@
 [first-contentful-image.html]
-  expected: TIMEOUT
   [First contentful paint fires due to image render.]
-    expected: TIMEOUT
+    expected: TIMEOUT # Expect timeout because we don't have FP
 
diff --git a/testing/web-platform/meta/paint-timing/first-contentful-paint.html.ini b/testing/web-platform/meta/paint-timing/with-first-paint/first-contentful-paint.html.ini
similarity index 69%
rename from testing/web-platform/meta/paint-timing/first-contentful-paint.html.ini
rename to testing/web-platform/meta/paint-timing/with-first-paint/first-contentful-paint.html.ini
index 133f8b52a4..6237153a7e 100644
--- a/testing/web-platform/meta/paint-timing/first-contentful-paint.html.ini
+++ b/testing/web-platform/meta/paint-timing/with-first-paint/first-contentful-paint.html.ini
@@ -1,5 +1,5 @@
 [first-contentful-paint.html]
   expected: TIMEOUT
   [First Paint triggered by non-contentful paint. Image load triggers First Contentful Paint.]
-    expected: TIMEOUT
+    expected: TIMEOUT # Expect timeout because we don't have FP
 
diff --git a/testing/web-platform/meta/paint-timing/first-contentful-svg.html.ini b/testing/web-platform/meta/paint-timing/with-first-paint/first-contentful-svg.html.ini
similarity index 59%
rename from testing/web-platform/meta/paint-timing/first-contentful-svg.html.ini
rename to testing/web-platform/meta/paint-timing/with-first-paint/first-contentful-svg.html.ini
index 5ada0053c9..b06143f5b6 100644
--- a/testing/web-platform/meta/paint-timing/first-contentful-svg.html.ini
+++ b/testing/web-platform/meta/paint-timing/with-first-paint/first-contentful-svg.html.ini
@@ -1,5 +1,5 @@
 [first-contentful-svg.html]
   expected: TIMEOUT
   [First contentful paint fires due to svg.]
-    expected: TIMEOUT
+    expected: TIMEOUT # Expect timeout because we don't have FP
 
diff --git a/testing/web-platform/meta/paint-timing/first-image-child.html.ini b/testing/web-platform/meta/paint-timing/with-first-paint/first-image-child.html.ini
similarity index 66%
rename from testing/web-platform/meta/paint-timing/first-image-child.html.ini
rename to testing/web-platform/meta/paint-timing/with-first-paint/first-image-child.html.ini
index e7bcf30783..db3d16cb38 100644
--- a/testing/web-platform/meta/paint-timing/first-image-child.html.ini
+++ b/testing/web-platform/meta/paint-timing/with-first-paint/first-image-child.html.ini
@@ -1,5 +1,5 @@
 [first-image-child.html]
   expected: TIMEOUT
   [Child iframe ignores paint-timing events fired from parent image rendering.]
-    expected: TIMEOUT
+    expected: TIMEOUT # Expect timeout because we don't have FP
 
diff --git a/testing/web-platform/meta/paint-timing/first-paint-bg-color.html.ini b/testing/web-platform/meta/paint-timing/with-first-paint/first-paint-bg-color.html.ini
similarity index 61%
rename from testing/web-platform/meta/paint-timing/first-paint-bg-color.html.ini
rename to testing/web-platform/meta/paint-timing/with-first-paint/first-paint-bg-color.html.ini
index a57a7982b6..eff9914c20 100644
--- a/testing/web-platform/meta/paint-timing/first-paint-bg-color.html.ini
+++ b/testing/web-platform/meta/paint-timing/with-first-paint/first-paint-bg-color.html.ini
@@ -1,5 +1,5 @@
 [first-paint-bg-color.html]
   expected: TIMEOUT
   [First paint fires due to background color. No FCP]
-    expected: TIMEOUT
+    expected: TIMEOUT # Expect timeout because we don't have FP
 
diff --git a/testing/web-platform/meta/paint-timing/first-paint-only.html.ini b/testing/web-platform/meta/paint-timing/with-first-paint/first-paint-only.html.ini
similarity index 65%
rename from testing/web-platform/meta/paint-timing/first-paint-only.html.ini
rename to testing/web-platform/meta/paint-timing/with-first-paint/first-paint-only.html.ini
index 747604e097..8de947878b 100644
--- a/testing/web-platform/meta/paint-timing/first-paint-only.html.ini
+++ b/testing/web-platform/meta/paint-timing/with-first-paint/first-paint-only.html.ini
@@ -1,5 +1,5 @@
 [first-paint-only.html]
   expected: TIMEOUT
   [Performance first paint timing entry exists. No first contentful paint.]
-    expected: TIMEOUT
+    expected: TIMEOUT # Expect timeout because we don't have FP
 
diff --git a/testing/web-platform/meta/paint-timing/mask-image.html.ini b/testing/web-platform/meta/paint-timing/with-first-paint/mask-image.html.ini
similarity index 60%
rename from testing/web-platform/meta/paint-timing/mask-image.html.ini
rename to testing/web-platform/meta/paint-timing/with-first-paint/mask-image.html.ini
index d82dfafdf4..953618f5cf 100644
--- a/testing/web-platform/meta/paint-timing/mask-image.html.ini
+++ b/testing/web-platform/meta/paint-timing/with-first-paint/mask-image.html.ini
@@ -1,3 +1,5 @@
 [mask-image.html]
+  expected: TIMEOUT
   [Mask image triggers First Contentful Paint.]
-    expected: FAIL
+    expected: TIMEOUT
+
diff --git a/testing/web-platform/meta/paint-timing/paint-visited.html.ini b/testing/web-platform/meta/paint-timing/with-first-paint/paint-visited.html.ini
similarity index 60%
rename from testing/web-platform/meta/paint-timing/paint-visited.html.ini
rename to testing/web-platform/meta/paint-timing/with-first-paint/paint-visited.html.ini
index 15741bed6d..cae3d16178 100644
--- a/testing/web-platform/meta/paint-timing/paint-visited.html.ini
+++ b/testing/web-platform/meta/paint-timing/with-first-paint/paint-visited.html.ini
@@ -1,5 +1,5 @@
 [paint-visited.html]
   expected: TIMEOUT
   [Visited-attack test to check existence of FP and FCP.]
-    expected: TIMEOUT
+    expected: TIMEOUT # Expect timeout because we don't have FP
 
diff --git a/testing/web-platform/meta/paint-timing/sibling-painting-first-image.html.ini b/testing/web-platform/meta/paint-timing/with-first-paint/sibling-painting-first-image.html.ini
similarity index 65%
rename from testing/web-platform/meta/paint-timing/sibling-painting-first-image.html.ini
rename to testing/web-platform/meta/paint-timing/with-first-paint/sibling-painting-first-image.html.ini
index 7ce0b00f1f..1ab1cd2b5a 100644
--- a/testing/web-platform/meta/paint-timing/sibling-painting-first-image.html.ini
+++ b/testing/web-platform/meta/paint-timing/with-first-paint/sibling-painting-first-image.html.ini
@@ -1,5 +1,5 @@
 [sibling-painting-first-image.html]
   expected: TIMEOUT
   [Frame ignores paint-timing events fired from sibling frame.]
-    expected: TIMEOUT
+    expected: TIMEOUT # Expect timeout because we don't have FP
 
diff --git a/testing/web-platform/meta/performance-timeline/case-sensitivity.any.js.ini b/testing/web-platform/meta/performance-timeline/case-sensitivity.any.js.ini
new file mode 100644
index 0000000000..d34a42cd10
--- /dev/null
+++ b/testing/web-platform/meta/performance-timeline/case-sensitivity.any.js.ini
@@ -0,0 +1,7 @@
+[case-sensitivity.any.html]
+  [getEntriesByName values are case sensitive]
+    expected:
+      if webrender and (os == "linux") and not debug: ["PASS", "FAIL"]
+
+
+[case-sensitivity.any.worker.html]
diff --git a/testing/web-platform/meta/performance-timeline/po-disconnect-removes-observed-types.any.js.ini b/testing/web-platform/meta/performance-timeline/po-disconnect-removes-observed-types.any.js.ini
new file mode 100644
index 0000000000..551dad0f29
--- /dev/null
+++ b/testing/web-platform/meta/performance-timeline/po-disconnect-removes-observed-types.any.js.ini
@@ -0,0 +1,8 @@
+[po-disconnect-removes-observed-types.any.worker.html]
+  [Types observed are forgotten when disconnect() is called.]
+    expected: FAIL
+
+
+[po-disconnect-removes-observed-types.any.html]
+  [Types observed are forgotten when disconnect() is called.]
+    expected: FAIL
diff --git a/testing/web-platform/meta/resource-timing/buffered-flag.any.js.ini b/testing/web-platform/meta/resource-timing/buffered-flag.any.js.ini
new file mode 100644
index 0000000000..e2b9600e9a
--- /dev/null
+++ b/testing/web-platform/meta/resource-timing/buffered-flag.any.js.ini
@@ -0,0 +1,7 @@
+[buffered-flag.any.worker.html]
+  [PerformanceObserver with buffered flag sees previous resource entries.]
+    expected:
+      if (os == "android") and not debug: FAIL
+
+
+[buffered-flag.any.html]
diff --git a/testing/web-platform/meta/user-timing/idlharness.any.js.ini b/testing/web-platform/meta/user-timing/idlharness.any.js.ini
index 46b3b7d3d5..bc4fbdadd0 100644
--- a/testing/web-platform/meta/user-timing/idlharness.any.js.ini
+++ b/testing/web-platform/meta/user-timing/idlharness.any.js.ini
@@ -17,6 +17,9 @@
   [PerformanceMark interface: attribute detail]
     expected: FAIL
 
+  [idl_test setup]
+    expected: FAIL
+
 
 [idlharness.any.worker.html]
   [PerformanceMeasure interface: attribute detail]
@@ -34,6 +37,9 @@
   [PerformanceMark interface: attribute detail]
     expected: FAIL
 
+  [idl_test setup]
+    expected: FAIL
+
 
 [idlharness.any.sharedworker.html]
   [PerformanceMeasure interface: attribute detail]
@@ -51,6 +57,9 @@
   [PerformanceMark interface: attribute detail]
     expected: FAIL
 
+  [idl_test setup]
+    expected: FAIL
+
 
 [idlharness.any.serviceworker.html]
   [PerformanceMeasure interface: attribute detail]
@@ -68,3 +77,5 @@
   [PerformanceMark interface: attribute detail]
     expected: FAIL
 
+  [idl_test setup]
+    expected: FAIL
diff --git a/testing/web-platform/tests/css/css-flexbox/dynamic-isize-change-001-ref.html b/testing/web-platform/tests/css/css-flexbox/dynamic-isize-change-001-ref.html
new file mode 100644
index 0000000000..58b34c43fe
--- /dev/null
+++ b/testing/web-platform/tests/css/css-flexbox/dynamic-isize-change-001-ref.html
@@ -0,0 +1,37 @@
+<!DOCTYPE html>
+<html>
+  <meta charset="utf-8">
+  <title>CSS Reference: Dynamic change to the inline-size of a container containing a inline-flex child</title>
+  <link rel="author" title="Ting-Yu Lin" href="mailto:tlin@mozilla.com">
+  <link rel="author" title="Mozilla" href="https://www.mozilla.org/">
+
+  <style>
+  #container {
+    border: 1px solid black;
+    font: 30px monospace;
+    width: 400px;
+  }
+  .inline-flex {
+    display: inline-flex;
+    width: 100px;
+    border: 1px solid gray;
+  }
+
+  .small {
+    display: flex;
+    align-items: flex-end;
+    font: 8px monospace;
+    background: pink;
+  }
+  </style>
+
+  <body>
+    <div id="container">
+      abc
+      <div class="inline-flex">
+        <div class="small">D</div>
+        <div>efg</div>
+      </div>
+    </div>
+  </body>
+</html>
diff --git a/testing/web-platform/tests/css/css-flexbox/dynamic-isize-change-001.html b/testing/web-platform/tests/css/css-flexbox/dynamic-isize-change-001.html
new file mode 100644
index 0000000000..cf4a030043
--- /dev/null
+++ b/testing/web-platform/tests/css/css-flexbox/dynamic-isize-change-001.html
@@ -0,0 +1,49 @@
+<!DOCTYPE html>
+<html>
+  <meta charset="utf-8">
+  <title>CSS Test: Dynamic change to the inline-size of a container containing a inline-flex child</title>
+  <link rel="author" title="Ting-Yu Lin" href="mailto:tlin@mozilla.com">
+  <link rel="author" title="Mozilla" href="https://www.mozilla.org/">
+  <link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1686961">
+  <link rel="match" href="dynamic-isize-change-001-ref.html">
+
+  <style>
+  #container {
+    border: 1px solid black;
+    font: 30px monospace;
+    width: 200px;
+  }
+  .inline-flex {
+    display: inline-flex;
+    width: 100px;
+    border: 1px solid gray;
+  }
+
+  .small {
+    display: flex;
+    align-items: flex-end;
+    font: 8px monospace;
+    background: pink;
+  }
+  </style>
+
+  <script>
+  function test() {
+    let container = document.getElementById("container");
+    container.offsetTop;
+
+    /* Change the width to trigger incremental reflow. */
+    container.style.width = "400px";
+  }
+  </script>
+
+  <body onload="test()">
+    <div id="container">
+      abc
+      <div class="inline-flex">
+        <div class="small">D</div>
+        <div>efg</div>
+      </div>
+    </div>
+  </body>
+</html>
diff --git a/testing/web-platform/tests/css/css-flexbox/dynamic-isize-change-002.html b/testing/web-platform/tests/css/css-flexbox/dynamic-isize-change-002.html
new file mode 100644
index 0000000000..cc859b73f9
--- /dev/null
+++ b/testing/web-platform/tests/css/css-flexbox/dynamic-isize-change-002.html
@@ -0,0 +1,40 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<title>CSS Flexbox Test: Dynamic change to the inline-size of a row flex container</title>
+<link rel="author" title="Ting-Yu Lin" href="mailto:tlin@mozilla.com">
+<link rel="author" title="Mozilla" href="https://www.mozilla.org/">
+<link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1700580">
+<link rel="match" href="../reference/ref-filled-green-100px-square.xht">
+<meta name="assert" content="This test verifies that the dynamic change to the flex container's inline-size triggers the reflow for flex items with percentage padding.">
+
+<style>
+#flexbox {
+  display: flex;
+  inline-size: 50px;
+  block-size: 100px;
+  background: red;
+}
+
+#flexbox > div {
+  box-sizing: border-box;
+
+  /* The following flex-basis and padding will give our flex item a content-box
+     inline-size of 25px, both before and after this test's dynamic change. */
+  flex-basis: 100%;
+  padding-right: calc(100% - 25px);
+  background: green;
+}
+</style>
+
+<p>Test passes if there is a filled green square and <strong>no red</strong>.</p>
+<div id="flexbox">
+  <div></div>
+</div>
+
+<script>
+/* Make sure the layout is up-to-date, which is essential to trigger the bug. */
+document.documentElement.offsetHeight;
+
+/* Change the flexbox's inline-size to trigger incremental reflow. */
+document.getElementById("flexbox").style.inlineSize = "100px";
+</script>
diff --git a/testing/web-platform/tests/css/css-flexbox/dynamic-isize-change-003.html b/testing/web-platform/tests/css/css-flexbox/dynamic-isize-change-003.html
new file mode 100644
index 0000000000..9df13e313f
--- /dev/null
+++ b/testing/web-platform/tests/css/css-flexbox/dynamic-isize-change-003.html
@@ -0,0 +1,43 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<title>CSS Flexbox Test: Dynamic change to the inline-size of a column flexbox container</title>
+<link rel="author" title="Ting-Yu Lin" href="mailto:tlin@mozilla.com">
+<link rel="author" title="Mozilla" href="https://www.mozilla.org/">
+<link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1700580">
+<link rel="match" href="../reference/ref-filled-green-100px-square.xht">
+<meta name="assert" content="This test verifies that the dynamic change to the flex container's inline-size triggers the reflow for flex items with percentage padding.">
+
+<style>
+#flexbox {
+  display: flex;
+  flex-direction: column;
+  inline-size: 50px;
+  block-size: 100px;
+  background: red;
+}
+
+#flexbox > div {
+  box-sizing: border-box;
+  flex-basis: 100px;
+
+  /* The following padding will give our flex item a content-box inline-size of
+     25px, both before and after this test's dynamic change. (Note that the
+     horizontal axis is the flex container's cross axis, so the item stretches
+     its width by default to fill the available space.) */
+  padding-right: calc(100% - 25px);
+  background: green;
+}
+</style>
+
+<p>Test passes if there is a filled green square and <strong>no red</strong>.</p>
+<div id="flexbox">
+  <div></div>
+</div>
+
+<script>
+/* Make sure the layout is up-to-date, which is essential to trigger the bug. */
+document.documentElement.offsetHeight;
+
+/* Change the flexbox's inline-size to trigger incremental reflow. */
+document.getElementById("flexbox").style.inlineSize = "100px";
+</script>
diff --git a/testing/web-platform/tests/css/css-flexbox/dynamic-isize-change-004.html b/testing/web-platform/tests/css/css-flexbox/dynamic-isize-change-004.html
new file mode 100644
index 0000000000..1627e32d96
--- /dev/null
+++ b/testing/web-platform/tests/css/css-flexbox/dynamic-isize-change-004.html
@@ -0,0 +1,42 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<title>CSS Flexbox Test: Dynamic change to the inline-size of a row flex container</title>
+<link rel="author" title="Ting-Yu Lin" href="mailto:tlin@mozilla.com">
+<link rel="author" title="Mozilla" href="https://www.mozilla.org/">
+<link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1700580">
+<link rel="stylesheet" href="/fonts/ahem.css">
+<link rel="match" href="../reference/ref-filled-green-100px-square.xht">
+<meta name="assert" content="This test verifies that the dynamic change to the flex container's inline-size triggers the reflow for flex items with percentage padding.">
+
+<style>
+#flexbox {
+  display: flex;
+  inline-size: 100px;
+  block-size: 100px;
+  font: 50px/1 Ahem;
+  color: green;
+  word-break: break-all;
+}
+
+#flexbox > div {
+  /* The following flex-basis and padding will give our flex item a border-box
+     inline-size of 100px, both before and after this test's dynamic
+     modification. */
+  flex-basis: 50%;
+  padding-right: calc(100px - 50%);
+  background: red;
+}
+</style>
+
+<p>Test passes if there is a filled green square and <strong>no red</strong>.</p>
+<div id="flexbox">
+  <div>XXXX</div>
+</div>
+
+<script>
+/* Make sure the layout is up-to-date, which is essential to trigger the bug. */
+document.documentElement.offsetHeight;
+
+/* Change the flexbox's inline-size to trigger incremental reflow. */
+document.getElementById("flexbox").style.inlineSize = "200px";
+</script>
diff --git a/testing/web-platform/tests/css/css-flexbox/fixed-table-layout-with-percentage-width-in-flex-item-ref.html b/testing/web-platform/tests/css/css-flexbox/fixed-table-layout-with-percentage-width-in-flex-item-ref.html
new file mode 100644
index 0000000000..8e3e616717
--- /dev/null
+++ b/testing/web-platform/tests/css/css-flexbox/fixed-table-layout-with-percentage-width-in-flex-item-ref.html
@@ -0,0 +1,64 @@
+<!DOCTYPE html>
+<html>
+  <meta charset="utf-8">
+  <title>CSS Flexbox Reference: Test flex items containing table-layout:fixed with percentage width</title>
+  <link rel="author" title="Daniel Holbert" href="mailto:dholbert@mozilla.com">
+  <link rel="author" title="Ting-Yu Lin" href="mailto:tlin@mozilla.com">
+  <link rel="author" title="Mozilla" href="https://www.mozilla.org">
+
+  <style>
+  .container {
+    display: flex;
+    width: 300px;
+    margin-bottom: 5px;
+    border: 1px solid black;
+    background: red;
+  }
+  .tbl {
+    width: 100%;
+    height: 30px;
+    border: 1px solid blue;
+    box-sizing: border-box;
+    background: lightgray;
+  }
+  </style>
+
+  <div class="container">
+    <div class="tbl"></div>
+  </div>
+
+  <div class="container">
+    <div class="tbl"></div>
+    <div class="tbl"></div>
+  </div>
+
+  <div class="container">
+    <div class="tbl"></div>
+    <div class="tbl"></div>
+    <div class="tbl"></div>
+  </div>
+
+  <div class="container">
+    <div class="tbl"></div>
+    <div class="tbl"></div>
+    <div class="tbl"></div>
+    <div class="tbl"></div>
+  </div>
+
+  <div class="container">
+    <div class="tbl"></div>
+    <div class="tbl"></div>
+    <div class="tbl"></div>
+    <div class="tbl"></div>
+    <div class="tbl"></div>
+  </div>
+
+  <div class="container">
+    <div class="tbl"></div>
+    <div class="tbl"></div>
+    <div class="tbl"></div>
+    <div class="tbl"></div>
+    <div class="tbl"></div>
+    <div class="tbl"></div>
+  </div>
+</html>
diff --git a/testing/web-platform/tests/css/css-flexbox/fixed-table-layout-with-percentage-width-in-flex-item.html b/testing/web-platform/tests/css/css-flexbox/fixed-table-layout-with-percentage-width-in-flex-item.html
new file mode 100644
index 0000000000..507e0e9fce
--- /dev/null
+++ b/testing/web-platform/tests/css/css-flexbox/fixed-table-layout-with-percentage-width-in-flex-item.html
@@ -0,0 +1,69 @@
+<!DOCTYPE html>
+<html>
+  <meta charset="utf-8">
+  <title>CSS Flexbox Test: Test flex items containing table-layout:fixed with percentage width</title>
+  <link rel="author" title="Daniel Holbert" href="mailto:dholbert@mozilla.com">
+  <link rel="author" title="Ting-Yu Lin" href="mailto:tlin@mozilla.com">
+  <link rel="author" title="Mozilla" href="https://www.mozilla.org">
+  <link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1469649">
+  <link rel="match" href="fixed-table-layout-with-percentage-width-in-flex-item-ref.html">
+  <meta name="assert" content="This test verifies that each flex item with a table descendant should have the the same definite post-flexing main size.">
+
+  <style>
+  .container {
+    display: flex;
+    width: 300px;
+    margin-bottom: 5px;
+    border: 1px solid black;
+    background: red;
+  }
+  .tbl {
+    display: table;
+    table-layout: fixed;
+    width: 100%;
+    height: 30px;
+    border: 1px solid blue;
+    box-sizing: border-box;
+    background: lightgray;
+  }
+  </style>
+
+  <div class="container">
+    <div><div class="tbl"></div></div>
+  </div>
+
+  <div class="container">
+    <div><div class="tbl"></div></div>
+    <div><div class="tbl"></div></div>
+  </div>
+
+  <div class="container">
+    <div><div class="tbl"></div></div>
+    <div><div class="tbl"></div></div>
+    <div><div class="tbl"></div></div>
+  </div>
+
+  <div class="container">
+    <div><div class="tbl"></div></div>
+    <div><div class="tbl"></div></div>
+    <div><div class="tbl"></div></div>
+    <div><div class="tbl"></div></div>
+  </div>
+
+  <div class="container">
+    <div><div class="tbl"></div></div>
+    <div><div class="tbl"></div></div>
+    <div><div class="tbl"></div></div>
+    <div><div class="tbl"></div></div>
+    <div><div class="tbl"></div></div>
+  </div>
+
+  <div class="container">
+    <div><div class="tbl"></div></div>
+    <div><div class="tbl"></div></div>
+    <div><div class="tbl"></div></div>
+    <div><div class="tbl"></div></div>
+    <div><div class="tbl"></div></div>
+    <div><div class="tbl"></div></div>
+  </div>
+</html>
diff --git a/testing/web-platform/tests/css/css-flexbox/flex-basis-011-ref.html b/testing/web-platform/tests/css/css-flexbox/flex-basis-011-ref.html
new file mode 100644
index 0000000000..8c9d248efa
--- /dev/null
+++ b/testing/web-platform/tests/css/css-flexbox/flex-basis-011-ref.html
@@ -0,0 +1,21 @@
+<!DOCTYPE html>
+<link rel="author" title="Sergio Villar Senin" href="mailto:svillar@igalia.com">
+<link href="support/flexbox.css" rel="stylesheet">
+<style>
+.flex-item {
+    flex: 1 0 auto;
+    height: 100%;
+    border: 1px solid blue;
+}
+</style>
+
+<div class="flexbox">
+    <div class="flexbox column">
+        <div class="flex-item">
+            <div>AAA</div>
+        </div>
+        <div class="flex-item">
+            <div>BBB</div>
+        </div>
+    </div>
+</div>
diff --git a/testing/web-platform/tests/css/css-flexbox/flex-basis-011.html b/testing/web-platform/tests/css/css-flexbox/flex-basis-011.html
new file mode 100644
index 0000000000..9edb5dc975
--- /dev/null
+++ b/testing/web-platform/tests/css/css-flexbox/flex-basis-011.html
@@ -0,0 +1,24 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<title>CSS Flexbox Test: % flex-basis should not cause engines to treat items as percentage sized</title>
+<link rel="author" title="Sergio Villar Senin" href="mailto:svillar@igalia.com">
+<link rel="help" href="http://www.w3.org/TR/css-flexbox-1/#flex-basis-property">
+<link href="support/flexbox.css" rel="stylesheet">
+<link rel="match" href="flex-basis-011-ref.html">
+<style>
+.flex-item {
+    flex: 1 0 100%;
+    border: 1px solid blue;
+}
+</style>
+
+<div class="flexbox">
+    <div class="flexbox column">
+        <div class="flex-item">
+            <div>AAA</div>
+        </div>
+        <div class="flex-item">
+            <div>BBB</div>
+        </div>
+    </div>
+</div>
diff --git a/testing/web-platform/tests/css/css-flexbox/flex-basis-012.html b/testing/web-platform/tests/css/css-flexbox/flex-basis-012.html
new file mode 100644
index 0000000000..b1adddeb23
--- /dev/null
+++ b/testing/web-platform/tests/css/css-flexbox/flex-basis-012.html
@@ -0,0 +1,9 @@
+<!DOCTYPE html>
+<link rel="help" href="https://bugs.chromium.org/p/chromium/issues/detail?id=1199632">
+<link rel="match" href="../reference/ref-filled-green-100px-square.xht">
+<p>Test passes if there is a filled green square and <strong>no red</strong>.</p>
+<div style="display: flex; flex-direction: column; width: 100px;">
+  <div style="display: flex; flex-direction: column; height: 100px; background: red;">
+    <div style="flex-basis: 100%; background: green;"></div>
+  </div>
+</div>
diff --git a/testing/web-platform/tests/css/css-flexbox/flexbox-baseline-nested-001-ref.html b/testing/web-platform/tests/css/css-flexbox/flexbox-baseline-nested-001-ref.html
new file mode 100644
index 0000000000..dd4e144b46
--- /dev/null
+++ b/testing/web-platform/tests/css/css-flexbox/flexbox-baseline-nested-001-ref.html
@@ -0,0 +1,26 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <title>CSS Reference: Baseline of nested flex containers with stretched textfield inside</title>
+    <link rel="author" title="Daniel Holbert" href="mailto:dholbert@mozilla.com">
+    <link rel="author" title="Mozilla" href="http://www.mozilla.org/">
+    <meta charset="utf-8">
+    <style>
+      .ib {
+        display: inline-block;
+      }
+      .innerFlex {
+        display: flex;
+        height: 200px;
+      }
+    </style>
+  </head>
+  <body>
+    abc
+    <div class="ib">
+      <div class="innerFlex">
+        <input value="def">
+      </div>
+    </div>
+  </body>
+</html>
diff --git a/testing/web-platform/tests/css/css-flexbox/flexbox-baseline-nested-001.html b/testing/web-platform/tests/css/css-flexbox/flexbox-baseline-nested-001.html
new file mode 100644
index 0000000000..57999e57ce
--- /dev/null
+++ b/testing/web-platform/tests/css/css-flexbox/flexbox-baseline-nested-001.html
@@ -0,0 +1,35 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <meta charset="utf-8">
+    <title>CSS Test: Baseline of nested flex containers with stretched textfield inside</title>
+    <link rel="author" title="Daniel Holbert" href="mailto:dholbert@mozilla.com">
+    <link rel="author" title="Mozilla" href="http://www.mozilla.org/">
+    <link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1672640">
+    <link rel="help" href="https://drafts.csswg.org/css-flexbox-1/#flex-baselines">
+    <link rel="match" href="flexbox-baseline-nested-001-ref.html">
+
+    <style>
+      .ib {
+        display: inline-block;
+      }
+      .outerFlex {
+        display: flex;
+      }
+      .innerFlex {
+        display: flex;
+        height: 200px;
+      }
+    </style>
+  </head>
+  <body>
+    abc
+    <div class="ib">
+      <div class="outerFlex">
+        <div class="innerFlex">
+          <input value="def">
+        </div>
+      </div>
+    </div>
+  </body>
+</html>
diff --git a/testing/web-platform/tests/css/css-grid/grid-with-content-dynamic-display-001.html b/testing/web-platform/tests/css/css-grid/grid-with-content-dynamic-display-001.html
new file mode 100644
index 0000000000..e9f121b000
--- /dev/null
+++ b/testing/web-platform/tests/css/css-grid/grid-with-content-dynamic-display-001.html
@@ -0,0 +1,50 @@
+<!doctype html>
+<html>
+<head>
+<meta charset="utf-8">
+<link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1740702">
+<link rel="match" href="../reference/ref-filled-green-100px-square-only.html">
+<style>
+  #grid {
+    display: grid;
+    width: 100px;
+    height: 100px;
+    background: red;
+  }
+
+  #initiallyHidden {
+    display: none;
+    width: 100px;
+    height: 100px;
+    background: green;
+  }
+</style>
+</head>
+<body>
+  <p>Test passes if there is a filled green square.</p>
+  <div id="grid">
+    <div>
+      <div>
+        <div>
+          <div id="initiallyHidden">
+          </div>
+        </div>
+      </div>
+    </div>
+  </div>
+  <script>
+  "use strict";
+
+  const grid = document.getElementById("grid");
+  const initiallyHidden = document.getElementById("initiallyHidden");
+  document.documentElement.offsetHeight; // Flush layout
+
+  // Fails in buggy Firefox build because it prevents reflows from happening
+  getComputedStyle(grid).getPropertyValue("grid-template-columns");
+
+  document.documentElement.offsetHeight; // Flush layout again
+
+  initiallyHidden.style.display = "block"; // This should trigger a reflow.
+  </script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/css/css-grid/grid-with-content-dynamic-display-002.html b/testing/web-platform/tests/css/css-grid/grid-with-content-dynamic-display-002.html
new file mode 100644
index 0000000000..02f536344d
--- /dev/null
+++ b/testing/web-platform/tests/css/css-grid/grid-with-content-dynamic-display-002.html
@@ -0,0 +1,50 @@
+<!doctype html>
+<html>
+<head>
+<meta charset="utf-8">
+<link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1740702">
+<link rel="match" href="../reference/ref-filled-green-100px-square-only.html">
+<style>
+  #grid {
+    display: grid;
+    width: 100px;
+    height: 90px;
+    background: red;
+  }
+
+  #initiallyHidden {
+    display: none;
+    width: 100px;
+    height: 100px;
+    background: green;
+  }
+</style>
+</head>
+<body>
+  <p>Test passes if there is a filled green square.</p>
+  <div id="grid">
+    <div>
+      <div>
+        <div>
+          <div id="initiallyHidden">
+          </div>
+        </div>
+      </div>
+    </div>
+  </div>
+  <script>
+  "use strict";
+
+  const grid = document.getElementById("grid");
+  const initiallyHidden = document.getElementById("initiallyHidden");
+  document.documentElement.offsetHeight; // Flush layout
+
+  // Fails in buggy Firefox build because it prevents reflows from happening
+  grid.style.paddingBottom = "10px";
+
+  document.documentElement.offsetHeight; // Flush layout again
+
+  initiallyHidden.style.display = "block"; // This should trigger a reflow.
+  </script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/css/css-grid/nested-grid-item-block-size-001-ref.html b/testing/web-platform/tests/css/css-grid/nested-grid-item-block-size-001-ref.html
new file mode 100644
index 0000000000..a037967e49
--- /dev/null
+++ b/testing/web-platform/tests/css/css-grid/nested-grid-item-block-size-001-ref.html
@@ -0,0 +1,27 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html><head>
+<style>
+.container {
+  list-style: none;
+  padding: 0px;
+  margin: 0px;
+}
+
+img {
+  block-size: 55vw;
+  aspect-ratio: 2/1;
+}
+</style>
+</head>
+<body>
+  <ul class="container">
+    <li>
+      <img src="support/colors-8x16.png">
+    </li>
+  </ul>
+</body>
+</html>
diff --git a/testing/web-platform/tests/css/css-grid/nested-grid-item-block-size-001.html b/testing/web-platform/tests/css/css-grid/nested-grid-item-block-size-001.html
new file mode 100644
index 0000000000..e2892ecc3c
--- /dev/null
+++ b/testing/web-platform/tests/css/css-grid/nested-grid-item-block-size-001.html
@@ -0,0 +1,37 @@
+<!DOCTYPE HTML>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html><head>
+  <link rel="author" title="Sean Feng" href="mailto:sefeng@mozilla.com">
+  <title>CSS Grid Test: Nested grid contains an item that overflows the viewport</title>
+  <link rel="help" href="https://drafts.csswg.org/css-grid">
+  <link rel="match" href="nested-grid-item-block-size-001-ref.html">
+<style>
+.container {
+  display: grid;
+  grid-auto-flow: column;
+  list-style: none;
+  padding: 0px;
+  margin: 0px;
+}
+
+img {
+  block-size: 55vw;
+  aspect-ratio: 2/1;
+}
+</style>
+</head>
+<body>
+  <ul class="container">
+    <li>
+      <div style="display: inline-block;">
+        <div style="display: grid;">
+          <img src="support/colors-8x16.png">
+        </div>
+      </div>
+    </li>
+  </ul>
+</body>
+</html>
diff --git a/testing/web-platform/tests/css/css-grid/support/colors-8x16.png b/testing/web-platform/tests/css/css-grid/support/colors-8x16.png
new file mode 100644
index 0000000000000000000000000000000000000000..596fdb389d6cedd10f54939edd07dacb0e615ac2
GIT binary patch
literal 92
zcmeAS@N?(olHy`uVBq!ia0vp^96&6<!2~3iyjZCPq?A2f977~7C#NL*IN!j~Qy?bH
q%x7Ss8u8EEM5!k5yg|rcMutfTm>2zS+uZ_G&fw|l=d#Wzp$P!Vi5Y4D

literal 0
HcmV?d00001

diff --git a/testing/web-platform/tests/css/css-overflow/overflow-empty-child-box.html b/testing/web-platform/tests/css/css-overflow/overflow-empty-child-box.html
new file mode 100644
index 0000000000..880e0d3684
--- /dev/null
+++ b/testing/web-platform/tests/css/css-overflow/overflow-empty-child-box.html
@@ -0,0 +1,59 @@
+<!DOCTYPE html>
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<html>
+  <meta charset="utf-8">
+  <title>CSS Overflow Test: Testing an empty child box and its container's scrollable overflow area</title>
+  <link rel="author" title="Ting-Yu Lin" href="mailto:tlin@mozilla.com">
+  <link rel="author" title="Mozilla" href="https://www.mozilla.org/">
+  <link rel="help" href="https://drafts.csswg.org/css-overflow-3/#scrollable">
+  <meta name="assert" content="This test verifies that an empty child box shouldn't contribute to its parents scrollable overflow area.">
+
+  <script src="/resources/testharness.js"></script>
+  <script src="/resources/testharnessreport.js"></script>
+  <script src="/resources/check-layout-th.js"></script>
+
+  <style>
+  .container {
+    border: 1px solid black;
+    width: 200px;
+    height: 100px;
+  }
+
+  .empty {
+    position: relative;
+    width: 0px;
+    height: 0px;
+    left: 500px;
+    top: 300px;
+    box-shadow: 0 0 0 10px blue;
+  }
+  </style>
+
+  <body onload="checkLayout('.container')">
+    <p>You should see no scrollbars in these container because an empty child
+    box shouldn't contribute to its parents scrollable overflow area. </p>
+
+    <div class="container" style="overflow: visible"
+         data-expected-scroll-width="200" data-expected-scroll-height="100">
+      <div class="empty"></div>
+    </div>
+
+    <div class="container" style="overflow: auto"
+         data-expected-scroll-width="200" data-expected-scroll-height="100">
+      <div class="empty"></div>
+    </div>
+
+    <div class="container" style="overflow: hidden"
+         data-expected-scroll-width="200" data-expected-scroll-height="100">
+      <div class="empty"></div>
+    </div>
+
+    <div class="container" style="overflow: clip"
+         data-expected-scroll-width="200" data-expected-scroll-height="100">
+      <div class="empty"></div>
+    </div>
+  </body>
+</html>
diff --git a/testing/web-platform/tests/css/css-pseudo/reference/selection-contenteditable-011-ref.html b/testing/web-platform/tests/css/css-pseudo/reference/selection-contenteditable-011-ref.html
new file mode 100644
index 0000000000..0677a4b6b3
--- /dev/null
+++ b/testing/web-platform/tests/css/css-pseudo/reference/selection-contenteditable-011-ref.html
@@ -0,0 +1,21 @@
+<!DOCTYPE html>
+
+  <meta charset="UTF-8">
+
+  <title>CSS Reftest Reference</title>
+
+  <link rel="author" title="Gérard Talbot" href="http://www.gtalbot.org/BrowserBugsSection/css21testsuite/">
+
+  <style>
+  div
+    {
+      background-color: yellow;
+      color: green;
+      display: inline;
+      font-size: 300%;
+    }
+  </style>
+
+  <p>Test passes if each glyph of "Selected Text" is green with a yellow background and if there is <strong>no red</strong>.
+
+  <div contenteditable="true" id="test">Selected Text</div>
diff --git a/testing/web-platform/tests/css/css-pseudo/reference/selection-input-011-ref.html b/testing/web-platform/tests/css/css-pseudo/reference/selection-input-011-ref.html
new file mode 100644
index 0000000000..b49b0b00fa
--- /dev/null
+++ b/testing/web-platform/tests/css/css-pseudo/reference/selection-input-011-ref.html
@@ -0,0 +1,24 @@
+<!DOCTYPE html>
+
+  <meta charset="UTF-8">
+
+  <title>CSS Reftest Reference</title>
+
+  <link rel="author" title="Gérard Talbot" href="http://www.gtalbot.org/BrowserBugsSection/css21testsuite/">
+
+  <style>
+  input
+    {
+      background-color: yellow;
+      color: green;
+      font-family: monospace;
+      font-size: 48px;
+      line-height: 56px;
+      padding: 0px;
+      width: 13ch;
+    }
+  </style>
+
+  <p>Test passes if each glyph of "Selected Text" is green with a yellow background and if there is <strong>no red</strong>.
+
+  <div><input type="text" value="Selected Text"></div>
diff --git a/testing/web-platform/tests/css/css-pseudo/reference/selection-intercharacter-011-ref.html b/testing/web-platform/tests/css/css-pseudo/reference/selection-intercharacter-011-ref.html
new file mode 100644
index 0000000000..b0c60408f7
--- /dev/null
+++ b/testing/web-platform/tests/css/css-pseudo/reference/selection-intercharacter-011-ref.html
@@ -0,0 +1,26 @@
+<!DOCTYPE html>
+
+  <meta charset="UTF-8">
+
+  <title>CSS Reftest Reference</title>
+
+  <link rel="author" title="Gérard Talbot" href="http://www.gtalbot.org/BrowserBugsSection/css21testsuite/">
+
+  <style>
+  div
+    {
+      background-color: yellow;
+      display: inline-block;
+      font-size: 48px;
+      letter-spacing: 1em;
+    }
+
+  span
+    {
+      background-color: orange;
+    }
+  </style>
+
+  <p>Test passes if the background of characters "c" and "t" is orange (and only those 2 characters) and if the space between those 2 characters is also orange.
+
+  <div>Sele<span>ct</span>ed Text</div>
diff --git a/testing/web-platform/tests/css/css-pseudo/reference/selection-intercharacter-012-ref.html b/testing/web-platform/tests/css/css-pseudo/reference/selection-intercharacter-012-ref.html
new file mode 100644
index 0000000000..38650c90b4
--- /dev/null
+++ b/testing/web-platform/tests/css/css-pseudo/reference/selection-intercharacter-012-ref.html
@@ -0,0 +1,26 @@
+<!DOCTYPE html>
+
+  <meta charset="UTF-8">
+
+  <title>CSS Reftest Reference</title>
+
+  <link rel="author" title="Gérard Talbot" href="http://www.gtalbot.org/BrowserBugsSection/css21testsuite/">
+
+  <style>
+  div
+    {
+      background-color: yellow;
+      display: inline-block;
+      font-size: 48px;
+      letter-spacing: 1em;
+    }
+
+  span
+    {
+      background-color: orange;
+    }
+  </style>
+
+  <p>Test passes if the background of characters "c" and "t" is orange and if the space between those 2 characters is yellow (and not orange).
+
+  <div>Sele<span>c</span> <span>t</span>ed Text</div>
diff --git a/testing/web-platform/tests/css/css-pseudo/reference/selection-textarea-011-ref.html b/testing/web-platform/tests/css/css-pseudo/reference/selection-textarea-011-ref.html
new file mode 100644
index 0000000000..5c78176d60
--- /dev/null
+++ b/testing/web-platform/tests/css/css-pseudo/reference/selection-textarea-011-ref.html
@@ -0,0 +1,27 @@
+<!DOCTYPE html>
+
+  <meta charset="UTF-8">
+
+  <title>CSS Reftest Reference</title>
+
+  <link rel="author" title="Gérard Talbot" href="http://www.gtalbot.org/BrowserBugsSection/css21testsuite/">
+
+  <style>
+  textarea
+    {
+      background-color: yellow;
+      color: green;
+      font-family: monospace;
+      font-size: 48px;
+      height: 112px;
+      line-height: 56px;
+      padding: 0px;
+      resize: none;
+      width: 8ch;
+      outline: none;
+    }
+  </style>
+
+  <p>Test passes if each glyph of both "Selected" is green with a yellow background and if there is <strong>no red</strong>.
+
+  <div><textarea rows="2" cols="8">Selected Selected </textarea></div>
diff --git a/testing/web-platform/tests/css/css-pseudo/selection-contenteditable-011.html b/testing/web-platform/tests/css/css-pseudo/selection-contenteditable-011.html
new file mode 100644
index 0000000000..bc01d103ea
--- /dev/null
+++ b/testing/web-platform/tests/css/css-pseudo/selection-contenteditable-011.html
@@ -0,0 +1,45 @@
+<!DOCTYPE html>
+
+  <meta charset="UTF-8">
+
+  <title>CSS Pseudo-Elements Test: active selection and contenteditable element</title>
+
+  <link rel="author" title="Gérard Talbot" href="http://www.gtalbot.org/BrowserBugsSection/css21testsuite/">
+  <link rel="help" href="https://www.w3.org/TR/css-pseudo-4/#highlight-selectors">
+  <link rel="match" href="reference/selection-contenteditable-011-ref.html">
+
+  <meta content="" name="flags">
+
+  <style>
+  div
+    {
+      background-color: red;
+      color: yellow;
+      display: inline;
+      font-size: 300%;
+    }
+
+  div::selection
+    {
+      background-color: yellow;
+      color: green;
+    }
+  </style>
+
+  <script>
+  function startTest()
+  {
+  var targetRange = document.createRange();
+  /* We first create an empty range */
+  targetRange.selectNodeContents(document.getElementById("test"));
+  /* Then we set the range boundaries to the children of div#test */
+  window.getSelection().addRange(targetRange);
+  /* Finally, we now select such range of content */
+  }
+  </script>
+
+  <body onload="startTest();">
+
+  <p>Test passes if each glyph of "Selected Text" is green with a yellow background and if there is <strong>no red</strong>.
+
+  <div contenteditable="true" id="test">Selected Text</div>
diff --git a/testing/web-platform/tests/css/css-pseudo/selection-input-011.html b/testing/web-platform/tests/css/css-pseudo/selection-input-011.html
new file mode 100644
index 0000000000..77f7188c71
--- /dev/null
+++ b/testing/web-platform/tests/css/css-pseudo/selection-input-011.html
@@ -0,0 +1,43 @@
+<!DOCTYPE html>
+
+  <meta charset="UTF-8">
+
+  <title>CSS Pseudo-Elements Test: active selection and input type="text" element</title>
+
+  <link rel="author" title="Gérard Talbot" href="http://www.gtalbot.org/BrowserBugsSection/css21testsuite/">
+  <link rel="help" href="https://www.w3.org/TR/css-pseudo-4/#highlight-selectors">
+  <link rel="match" href="reference/selection-input-011-ref.html">
+
+  <meta content="" name="flags">
+
+  <style>
+  input
+    {
+      background-color: red;
+      color: yellow;
+      font-family: monospace;
+      font-size: 48px;
+      line-height: 56px;
+      padding: 0px;
+      width: 13ch;
+    }
+
+  input::selection
+    {
+      background-color: yellow;
+      color: green;
+    }
+  </style>
+
+  <script>
+  function startTest()
+  {
+  document.getElementById("test").select();
+  }
+  </script>
+
+  <body onload="startTest();">
+
+  <p>Test passes if each glyph of "Selected Text" is green with a yellow background and if there is <strong>no red</strong>.
+
+  <div><input type="text" value="Selected Text" id="test"></div>
diff --git a/testing/web-platform/tests/css/css-pseudo/selection-intercharacter-011.html b/testing/web-platform/tests/css/css-pseudo/selection-intercharacter-011.html
new file mode 100644
index 0000000000..70ab69fb49
--- /dev/null
+++ b/testing/web-platform/tests/css/css-pseudo/selection-intercharacter-011.html
@@ -0,0 +1,49 @@
+<!DOCTYPE html>
+
+  <meta charset="UTF-8">
+
+  <title>CSS Pseudo-Elements Test: active selection and inter-character spacing</title>
+
+  <link rel="author" title="Gérard Talbot" href="http://www.gtalbot.org/BrowserBugsSection/css21testsuite/">
+  <link rel="help" href="https://www.w3.org/TR/css-pseudo-4/#highlight-bounds">
+  <link rel="help" href="https://www.w3.org/TR/css-text-3/#letter-spacing-property">
+  <link rel="match" href="reference/selection-intercharacter-011-ref.html">
+
+  <meta content="may" name="flags">
+  <meta name="assert" content="This test verifies that intercharacter spacing may be part of the overlay area. When intercharacter spacing is part of the overlay area, then it belongs to the innermost element which contains both characters and which contains such spacing when both characters are selected. In this test, the 'c' and the 't' characters and the space between these characters belong to the same element. Therefore, the 'c' character, the 't' character and the space between these characters have the same orange background color painting.">
+
+  <style>
+  div
+    {
+      font-size: 48px;
+      letter-spacing: 1em;
+    }
+
+  div::selection
+    {
+      background-color: yellow;
+    }
+
+  span::selection
+    {
+      background-color: orange;
+    }
+  </style>
+
+  <script>
+  function startTest()
+  {
+  var targetRange = document.createRange();
+  /* We first create an empty range */
+  targetRange.selectNodeContents(document.getElementById("test"));
+  /* Then we set the range boundaries to the children of div#test */
+  window.getSelection().addRange(targetRange);
+  /* Finally, we now select such range of content */
+  }
+  </script>
+
+  <body onload="startTest();">
+
+  <p>Test passes if the background of characters "c" and "t" is orange (and only those 2 characters) and if the space between those 2 characters is also orange.
+
+  <div id="test">Sele<span>ct</span>ed Text</div>
diff --git a/testing/web-platform/tests/css/css-pseudo/selection-intercharacter-012.html b/testing/web-platform/tests/css/css-pseudo/selection-intercharacter-012.html
new file mode 100644
index 0000000000..a04fc33e2f
--- /dev/null
+++ b/testing/web-platform/tests/css/css-pseudo/selection-intercharacter-012.html
@@ -0,0 +1,49 @@
+<!DOCTYPE html>
+
+  <meta charset="UTF-8">
+
+  <title>CSS Pseudo-Elements Test: active selection and inter-character spacing</title>
+
+  <link rel="author" title="Gérard Talbot" href="http://www.gtalbot.org/BrowserBugsSection/css21testsuite/">
+  <link rel="help" href="https://www.w3.org/TR/css-pseudo-4/#highlight-bounds">
+  <link rel="help" href="https://www.w3.org/TR/css-text-3/#letter-spacing-property">
+  <link rel="match" href="reference/selection-intercharacter-012-ref.html">
+
+  <meta content="may" name="flags">
+  <meta name="assert" content="In this test, the 'c' and the 't' characters share the same level in the containment hierarchy but the space between these characters does not. Therefore, only the 'c' and the 't' characters themselves have an orange background color painting.">
+
+  <style>
+  div
+    {
+      font-size: 48px;
+      letter-spacing: 1em;
+    }
+
+  div::selection
+    {
+      background-color: yellow;
+    }
+
+  span::selection
+    {
+      background-color: orange;
+    }
+  </style>
+
+  <script>
+  function startTest()
+  {
+  var targetRange = document.createRange();
+  /* We first create an empty range */
+  targetRange.selectNodeContents(document.getElementById("test"));
+  /* Then we set the range boundaries to the children of div#test */
+  window.getSelection().addRange(targetRange);
+  /* Finally, we now select such range of content */
+  }
+  </script>
+
+  <body onload="startTest();">
+
+  <p>Test passes if the background of characters "c" and "t" is orange and if the space between those 2 characters is yellow (and not orange).
+
+  <div id="test">Sele<span>c</span> <span>t</span>ed Text</div>
diff --git a/testing/web-platform/tests/css/css-pseudo/selection-textarea-011.html b/testing/web-platform/tests/css/css-pseudo/selection-textarea-011.html
new file mode 100644
index 0000000000..4a925bae33
--- /dev/null
+++ b/testing/web-platform/tests/css/css-pseudo/selection-textarea-011.html
@@ -0,0 +1,46 @@
+<!DOCTYPE html>
+
+  <meta charset="UTF-8">
+
+  <title>CSS Pseudo-Elements Test: active selection and textarea element</title>
+
+  <link rel="author" title="Gérard Talbot" href="http://www.gtalbot.org/BrowserBugsSection/css21testsuite/">
+  <link rel="help" href="https://www.w3.org/TR/css-pseudo-4/#highlight-selectors">
+  <link rel="match" href="reference/selection-textarea-011-ref.html">
+
+  <meta content="" name="flags">
+
+  <style>
+  textarea
+    {
+      background-color: red;
+      color: yellow;
+      font-family: monospace;
+      font-size: 48px;
+      height: 112px;
+      line-height: 56px;
+      padding: 0px;
+      resize: none;
+      width: 8ch;
+      outline: none;
+    }
+
+  textarea::selection
+    {
+      background-color: yellow;
+      color: green;
+    }
+  </style>
+
+  <script>
+  function startTest()
+  {
+  document.getElementById("test").select();
+  }
+  </script>
+
+  <body onload="startTest();">
+
+  <p>Test passes if each glyph of both "Selected" is green with a yellow background and if there is <strong>no red</strong>.
+
+  <div><textarea id="test" rows="2" cols="8">Selected Selected </textarea></div>
diff --git a/testing/web-platform/tests/css/selectors/focus-visible-003-manual.html b/testing/web-platform/tests/css/selectors/focus-visible-003.html
similarity index 86%
rename from testing/web-platform/tests/css/selectors/focus-visible-003-manual.html
rename to testing/web-platform/tests/css/selectors/focus-visible-003.html
index eeb2904d7d..4620c1e411 100644
--- a/testing/web-platform/tests/css/selectors/focus-visible-003-manual.html
+++ b/testing/web-platform/tests/css/selectors/focus-visible-003.html
@@ -7,6 +7,9 @@
   <link rel="help" href="https://drafts.csswg.org/selectors-4/#the-focus-visible-pseudo" />
   <script src="/resources/testharness.js"></script>
   <script src="/resources/testharnessreport.js"></script>
+  <script src="/resources/testdriver.js"></script>
+  <script src="/resources/testdriver-actions.js"></script>
+  <script src="/resources/testdriver-vendor.js"></script>
   <style>
     :focus-visible {
       outline: red dotted 1px; /* fallback for Edge */
@@ -40,7 +43,7 @@
     <button data-tested="false" id="el-4">Focus me</span>
   </div>
   <div>
-    <input data-tested="false" id="el-5" type="button" value="Focus me"</input>
+    <input data-tested="false" id="el-5" type="button" value="Focus me"></input>
   </div>
   <div>
     <input data-tested="false" id="el-6" type="image" alt="Focus me."></input>
@@ -57,9 +60,6 @@
   <div>
     <label><input data-tested="false" id="el-10" type="radio"></input> Focus me.</label>
   </div>
-  <div>
-    <label><input data-tested="false" id="el-11" type="color"></input> Focus me.</label>
-  </div>
   <div>
     <!-- Focusing file input triggers a modal, so only test manually -->
     <input id="el-12" type="file" value="Focus me."></input>
@@ -67,7 +67,16 @@
   <div>
     <label><input data-tested="false" id="el-13" type="range"></input> Focus me.</label>
   </div>
+  <div>
+    <!-- Ensure the color input is last, as it has a pop-up which obscures other elements -->
+    <label><input data-tested="false" id="el-11" type="color"></input> Focus me.</label>
+  </div>
   <script>
+    function mouseClickInTarget(selector) {
+       let target = document.querySelector(selector);
+       return test_driver.click(target);
+    }
+
     async_test(function(t) {
         document.querySelectorAll("[data-tested]").forEach((el) => {
             el.addEventListener("click", t.step_func((e) => {
@@ -81,6 +90,8 @@
                 }
             }));
         });
+
+        mouseClickInTarget("[data-tested=false]");
     }, "Mouse focus on input elements which do not show a virtual keyboard should NOT match :focus-visible");
   </script>
 </body>
diff --git a/testing/web-platform/tests/css/selectors/focus-visible-004-manual.html b/testing/web-platform/tests/css/selectors/focus-visible-004-manual.html
index dba057cc9c..4d7878e751 100644
--- a/testing/web-platform/tests/css/selectors/focus-visible-004-manual.html
+++ b/testing/web-platform/tests/css/selectors/focus-visible-004-manual.html
@@ -57,9 +57,6 @@
   <div>
     <label><input data-tested="false" id="el-10" type="radio"></input> Focus me.</label>
   </div>
-  <div>
-    <label><input data-tested="false" id="el-11" type="color"></input> Focus me.</label>
-  </div>
   <div>
     <!-- Focusing file input triggers a modal, so only test manually -->
     <input id="el-12" type="file" value="Focus me."></input>
@@ -67,6 +64,12 @@
   <div>
     <label><input data-tested="false" id="el-13" type="range"></input> Focus me.</label>
   </div>
+  <div>
+    <!-- Ensure the color input is last, as it has a pop-up which obscures other elements,
+         causing the `mouseClickInTarget` method to fail and the test to hang waiting for
+         a click event.-->
+    <label><input data-tested="false" id="el-11" type="color"></input> Focus me.</label>
+  </div>
   <script>
     async_test(function(t) {
         document.querySelectorAll("[data-tested]").forEach((el) => {
diff --git a/testing/web-platform/tests/element-timing/buffered-flag.html b/testing/web-platform/tests/element-timing/buffered-flag.html
new file mode 100644
index 0000000000..19c387d26b
--- /dev/null
+++ b/testing/web-platform/tests/element-timing/buffered-flag.html
@@ -0,0 +1,42 @@
+<!DOCTYPE HTML>
+<meta charset=utf-8>
+<title>Element Timing: observe element with buffered flag</title>
+<body>
+<style>
+body {
+  margin: 0;
+}
+</style>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="resources/element-timing-helpers.js"></script>
+<script>
+  async_test(t => {
+    const beforeRender = performance.now();
+    const img = document.createElement('img');
+    if (!window.PerformanceElementTiming) {
+      assert_unreached("PerformanceElementTiming is not implemented");
+    }
+    // Initial observer used to know when entry has been dispatched
+    new PerformanceObserver(() => {
+      // Second observer should require buffered flag to receive the already-dispatched entry.
+      new PerformanceObserver(t.step_func_done(entryList => {
+        assert_equals(entryList.getEntries().length, 1);
+        const entry = entryList.getEntries()[0];
+        const pathname = window.location.origin + '/images/black-rectangle.png';
+        checkElement(entry, pathname, 'my_image', 'my_id', beforeRender, document.getElementById('my_id'));
+        // Test that viewport size is at least 100, so element is fully visible.
+        assert_greater_than_equal(document.documentElement.clientWidth, 100, 'Width should be >= 100');
+        assert_greater_than_equal(document.documentElement.clientHeight, 100, 'Height should be >= 100');
+
+        checkRect(entry, [0, 100, 0, 50]);
+        checkNaturalSize(entry, 100, 50);
+      })).observe({type: 'element', buffered: true});
+    }).observe({type: 'element'});
+    img.src = '/images/black-rectangle.png';
+    img.setAttribute('elementtiming', 'my_image');
+    img.setAttribute('id', 'my_id');
+    document.body.appendChild(img);
+  }, 'Element Timing entries are observable via buffered flag.');
+</script>
+</body>
diff --git a/testing/web-platform/tests/2dcontext/drawing-paths-to-the-canvas/canvas_focus_drawFocusIfNeeded_AAPI_001-manual.html b/testing/web-platform/tests/html/canvas/element/manual/drawing-paths-to-the-canvas/canvas_focus_drawFocusIfNeeded_AAPI_001-manual.html
similarity index 100%
rename from testing/web-platform/tests/2dcontext/drawing-paths-to-the-canvas/canvas_focus_drawFocusIfNeeded_AAPI_001-manual.html
rename to testing/web-platform/tests/html/canvas/element/manual/drawing-paths-to-the-canvas/canvas_focus_drawFocusIfNeeded_AAPI_001-manual.html
diff --git a/testing/web-platform/tests/2dcontext/drawing-paths-to-the-canvas/drawFocusIfNeeded_001.html b/testing/web-platform/tests/html/canvas/element/manual/drawing-paths-to-the-canvas/drawFocusIfNeeded_001.html
similarity index 100%
rename from testing/web-platform/tests/2dcontext/drawing-paths-to-the-canvas/drawFocusIfNeeded_001.html
rename to testing/web-platform/tests/html/canvas/element/manual/drawing-paths-to-the-canvas/drawFocusIfNeeded_001.html
diff --git a/testing/web-platform/tests/2dcontext/drawing-paths-to-the-canvas/drawFocusIfNeeded_002.html b/testing/web-platform/tests/html/canvas/element/manual/drawing-paths-to-the-canvas/drawFocusIfNeeded_002.html
similarity index 100%
rename from testing/web-platform/tests/2dcontext/drawing-paths-to-the-canvas/drawFocusIfNeeded_002.html
rename to testing/web-platform/tests/html/canvas/element/manual/drawing-paths-to-the-canvas/drawFocusIfNeeded_002.html
diff --git a/testing/web-platform/tests/2dcontext/drawing-paths-to-the-canvas/drawFocusIfNeeded_003.html b/testing/web-platform/tests/html/canvas/element/manual/drawing-paths-to-the-canvas/drawFocusIfNeeded_003.html
similarity index 100%
rename from testing/web-platform/tests/2dcontext/drawing-paths-to-the-canvas/drawFocusIfNeeded_003.html
rename to testing/web-platform/tests/html/canvas/element/manual/drawing-paths-to-the-canvas/drawFocusIfNeeded_003.html
diff --git a/testing/web-platform/tests/2dcontext/drawing-paths-to-the-canvas/drawFocusIfNeeded_004.html b/testing/web-platform/tests/html/canvas/element/manual/drawing-paths-to-the-canvas/drawFocusIfNeeded_004.html
similarity index 100%
rename from testing/web-platform/tests/2dcontext/drawing-paths-to-the-canvas/drawFocusIfNeeded_004.html
rename to testing/web-platform/tests/html/canvas/element/manual/drawing-paths-to-the-canvas/drawFocusIfNeeded_004.html
diff --git a/testing/web-platform/tests/2dcontext/drawing-paths-to-the-canvas/drawFocusIfNeeded_005.html b/testing/web-platform/tests/html/canvas/element/manual/drawing-paths-to-the-canvas/drawFocusIfNeeded_005.html
similarity index 100%
rename from testing/web-platform/tests/2dcontext/drawing-paths-to-the-canvas/drawFocusIfNeeded_005.html
rename to testing/web-platform/tests/html/canvas/element/manual/drawing-paths-to-the-canvas/drawFocusIfNeeded_005.html
diff --git a/testing/web-platform/tests/interfaces/user-timing.idl b/testing/web-platform/tests/interfaces/user-timing.idl
index cd2e1446b8..4130803ff9 100644
--- a/testing/web-platform/tests/interfaces/user-timing.idl
+++ b/testing/web-platform/tests/interfaces/user-timing.idl
@@ -4,23 +4,23 @@
 // Source: User Timing Level 3 (https://w3c.github.io/user-timing/)
 
 dictionary PerformanceMarkOptions {
-    any detail = null;
-    DOMHighResTimeStamp startTime;
-};
+            any detail;
+            DOMHighResTimeStamp startTime;
+        };
 
-dictionary PerformanceMeasureOptions {
-    any detail = null;
-    (DOMString or DOMHighResTimeStamp) start;
-    DOMHighResTimeStamp duration;
-    (DOMString or DOMHighResTimeStamp) end;
-};
+        dictionary PerformanceMeasureOptions {
+            any detail;
+            (DOMString or DOMHighResTimeStamp) start;
+            DOMHighResTimeStamp duration;
+            (DOMString or DOMHighResTimeStamp) end;
+        };
 
-partial interface Performance {
-    PerformanceMark mark(DOMString markName, optional PerformanceMarkOptions markOptions);
-    void clearMarks(optional DOMString markName);
-    PerformanceMeasure measure(DOMString measureName, optional (DOMString or PerformanceMeasureOptions)? startOrMeasureOptions, optional DOMString endMark);
-    void clearMeasures(optional DOMString measureName);
-};
+        partial interface Performance {
+            PerformanceMark mark(DOMString markName, optional PerformanceMarkOptions markOptions = {});
+            void clearMarks(optional DOMString markName);
+            PerformanceMeasure measure(DOMString measureName, optional (DOMString or PerformanceMeasureOptions) startOrMeasureOptions = {}, optional DOMString endMark);
+            void clearMeasures(optional DOMString measureName);
+        };
 
 [Exposed=(Window,Worker),
  Constructor(DOMString markName, optional PerformanceMarkOptions markOptions)]
diff --git a/testing/web-platform/tests/longtask-timing/buffered-flag.window.js b/testing/web-platform/tests/longtask-timing/buffered-flag.window.js
new file mode 100644
index 0000000000..88e1363beb
--- /dev/null
+++ b/testing/web-platform/tests/longtask-timing/buffered-flag.window.js
@@ -0,0 +1,26 @@
+async_test(t => {
+    assert_implements(window.PerformanceLongTaskTiming, 'Longtasks are not supported.');
+    new PerformanceObserver(t.step_func((entryList, obs) => {
+        const observer = new PerformanceObserver(t.step_func_done(list => {
+            let longtaskObserved = false;
+            list.getEntries().forEach(entry => {
+                if (entry.entryType === 'mark')
+                    return;
+                assert_equals(entry.entryType, 'longtask');
+                assert_equals(entry.name, 'self');
+                assert_greater_than(entry.duration, 50);
+                longtaskObserved = true;
+            });
+            assert_true(longtaskObserved, 'Did not observe buffered longtask.');
+        }));
+        observer.observe({type: 'longtask', buffered: true});
+        // Observer mark so that we can flush the observer callback.
+        observer.observe({type: 'mark'});
+        performance.mark('m');
+        // Disconnect the embedding observer so this callback only runs once.
+        obs.disconnect();
+    })).observe({entryTypes: ['longtask']});
+    // Create a long task.
+    const begin = window.performance.now();
+    while (window.performance.now() < begin + 60);
+}, 'PerformanceObserver with buffered flag can see previous longtask entries.');
diff --git a/testing/web-platform/tests/longtask-timing/containerTypes.html b/testing/web-platform/tests/longtask-timing/containerTypes.html
new file mode 100644
index 0000000000..5a703f3995
--- /dev/null
+++ b/testing/web-platform/tests/longtask-timing/containerTypes.html
@@ -0,0 +1,64 @@
+<!DOCTYPE HTML>
+<meta charset=utf-8>
+<title>LongTask Timing: long tasks in various containers</title>
+<body>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<h1>Longtasks in iframe, frame, object, and embed</h1>
+<div id="log"></div>
+<script>
+function Container(name, src) {
+    this.name = name;
+    this.src = src;
+}
+const Containers = [
+    new Container('iframe', 'src'),
+    new Container('frame', 'src'),
+    new Container('object', 'data'),
+    new Container('embed', 'src'),
+];
+Containers.forEach(container => {
+  promise_test(async t => {
+    assert_implements(window.PerformanceLongTaskTiming, 'Longtasks are not supported.');
+    const initialTime = performance.now();
+    return new Promise(resolve => {
+      const observer = new PerformanceObserver(t.step_func(entryList => {
+        const entries = entryList.getEntries();
+        assert_equals(entries.length, 1,
+          'Exactly one entry is expected.');
+        const longtask = entries[0];
+        assert_equals(longtask.entryType, 'longtask');
+        if (longtask.name == 'self' ||
+            longtask.name == 'multiple-contexts' ||
+            longtask.name == 'unknown')
+          return;
+        assert_equals(longtask.name, 'same-origin-descendant');
+        assert_greater_than(longtask.duration, 50);
+        assert_greater_than_equal(longtask.startTime, initialTime);
+        const currentTime = performance.now();
+        assert_less_than_equal(longtask.startTime, currentTime);
+        // Assert the TaskAttributionTiming entry in attribution.
+        assert_equals(longtask.attribution.length, 1,
+          'Exactly one attribution entry is expected');
+        const attribution = longtask.attribution[0];
+        assert_equals(attribution.entryType, 'taskattribution');
+        assert_equals(attribution.name, 'unknown');
+        assert_equals(attribution.duration, 0);
+        assert_equals(attribution.startTime, 0);
+        assert_equals(attribution.containerId, container.name + '-id');
+        assert_equals(attribution.containerName, container.name + '-name');
+        assert_equals(attribution.containerSrc, 'resources/subframe-with-longtask.html');
+        observer.disconnect();
+        resolve();
+      }));
+      observer.observe({entryTypes: ['longtask']});
+      const containerObject = document.createElement(container.name);
+      containerObject.id = container.name + '-id';
+      containerObject.name = container.name + '-name';
+      containerObject[container.src] = 'resources/subframe-with-longtask.html';
+      document.body.appendChild(containerObject);
+    });
+  }, `Performance longtask entries in ${container.name} are observable in parent.`);
+});
+</script>
+</body>
diff --git a/testing/web-platform/tests/longtask-timing/long-microtask.window.js b/testing/web-platform/tests/longtask-timing/long-microtask.window.js
new file mode 100644
index 0000000000..ef16f00dbe
--- /dev/null
+++ b/testing/web-platform/tests/longtask-timing/long-microtask.window.js
@@ -0,0 +1,26 @@
+async_test(function (t) {
+    assert_implements(window.PerformanceLongTaskTiming, 'Longtasks are not supported.');
+    new PerformanceObserver(
+        t.step_func_done(entryList => {
+            const entries = entryList.getEntries();
+            assert_equals(entries.length, 1,
+                'Exactly one entry is expected.');
+            const longtask = entries[0];
+            assert_equals(longtask.entryType, 'longtask');
+            assert_equals(longtask.name, 'self');
+            assert_greater_than(longtask.duration, 50);
+            assert_greater_than_equal(longtask.startTime, 0);
+            const currentTime = performance.now();
+            assert_less_than_equal(longtask.startTime, currentTime);
+            t.done();
+        })
+    ).observe({entryTypes: ['longtask']});
+
+    window.onload = () => {
+        /* Generate a slow microtask */
+        Promise.resolve().then(() => {
+            const begin = window.performance.now();
+            while (window.performance.now() < begin + 60);
+        });
+    };
+}, 'A short task followed by a long microtask is observable.');
diff --git a/testing/web-platform/tests/longtask-timing/longtask-attributes.html b/testing/web-platform/tests/longtask-timing/longtask-attributes.html
index b5d44b0db5..9af1c7bf95 100644
--- a/testing/web-platform/tests/longtask-timing/longtask-attributes.html
+++ b/testing/web-platform/tests/longtask-timing/longtask-attributes.html
@@ -10,10 +10,7 @@
 <div id="log"></div>
 <script>
   async_test(function (t) {
-    if (typeof PerformanceLongTaskTiming === 'undefined') {
-        assert_unreached("Longtasks are not supported.");
-        t.done();
-    }
+    assert_implements(window.PerformanceLongTaskTiming, 'Longtasks are not supported.');
     const observer = new PerformanceObserver(
         t.step_func(function (entryList) {
             const entries = entryList.getEntries();
@@ -35,6 +32,7 @@
             assert_equals(attribution.name, 'unknown');
             assert_equals(attribution.duration, 0);
             assert_equals(attribution.startTime, 0);
+            assert_equals(attribution.containerType, 'window');
             assert_equals(attribution.containerId, '');
             assert_equals(attribution.containerName, '');
             assert_equals(attribution.containerSrc, '');
diff --git a/testing/web-platform/tests/longtask-timing/longtask-in-childiframe-crossorigin.html b/testing/web-platform/tests/longtask-timing/longtask-in-childiframe-crossorigin.html
index aaabce5d79..d0fdf74280 100644
--- a/testing/web-platform/tests/longtask-timing/longtask-in-childiframe-crossorigin.html
+++ b/testing/web-platform/tests/longtask-timing/longtask-in-childiframe-crossorigin.html
@@ -10,10 +10,7 @@
 <div id="log"></div>
 <script>
   async_test(function (t) {
-    if (typeof PerformanceLongTaskTiming === 'undefined') {
-        assert_unreached("Longtasks are not supported.");
-        t.done();
-    }
+    assert_implements(window.PerformanceLongTaskTiming, 'Longtasks are not supported.');
     const observer = new PerformanceObserver(
         t.step_func(function (entryList) {
             const entries = entryList.getEntries();
@@ -36,6 +33,7 @@
             assert_equals(attribution.name, 'unknown');
             assert_equals(attribution.duration, 0);
             assert_equals(attribution.startTime, 0);
+            assert_equals(attribution.containerType, 'iframe');
             assert_equals(attribution.containerId, 'child-iframe-id');
             assert_equals(attribution.containerName, 'child-iframe-name');
             assert_equals(attribution.containerSrc,
diff --git a/testing/web-platform/tests/longtask-timing/longtask-in-childiframe.html b/testing/web-platform/tests/longtask-timing/longtask-in-childiframe.html
index 34b802cb69..4c325c42ad 100644
--- a/testing/web-platform/tests/longtask-timing/longtask-in-childiframe.html
+++ b/testing/web-platform/tests/longtask-timing/longtask-in-childiframe.html
@@ -11,10 +11,7 @@
 <script>
   const initialTime = performance.now();
   async_test(function (t) {
-    if (typeof PerformanceLongTaskTiming === 'undefined') {
-        assert_unreached("Longtasks are not supported.");
-        t.done();
-    }
+    assert_implements(window.PerformanceLongTaskTiming, 'Longtasks are not supported.');
     const observer = new PerformanceObserver(
         t.step_func(function (entryList) {
             const entries = entryList.getEntries();
@@ -41,6 +38,7 @@
             assert_equals(attribution.name, 'unknown');
             assert_equals(attribution.duration, 0);
             assert_equals(attribution.startTime, 0);
+            assert_equals(attribution.containerType, 'iframe');
             assert_equals(attribution.containerId, 'child-iframe-id');
             assert_equals(attribution.containerName, 'child-iframe-name');
             assert_equals(attribution.containerSrc, 'resources/subframe-with-longtask.html');
diff --git a/testing/web-platform/tests/longtask-timing/longtask-in-externalscript.html b/testing/web-platform/tests/longtask-timing/longtask-in-externalscript.html
index 076f0f2291..8636025cf2 100644
--- a/testing/web-platform/tests/longtask-timing/longtask-in-externalscript.html
+++ b/testing/web-platform/tests/longtask-timing/longtask-in-externalscript.html
@@ -10,10 +10,7 @@
 <div id="log"></div>
 <script>
   async_test(function (t) {
-    if (typeof PerformanceLongTaskTiming === 'undefined') {
-        assert_unreached("Longtasks are not supported.");
-        t.done();
-    }
+    assert_implements(window.PerformanceLongTaskTiming, 'Longtasks are not supported.');
     const observer = new PerformanceObserver(
         t.step_func(function (entryList) {
             const entries = entryList.getEntries();
@@ -32,6 +29,7 @@
             assert_equals(attribution.name, 'unknown');
             assert_equals(attribution.duration, 0);
             assert_equals(attribution.startTime, 0);
+            assert_equals(attribution.containerType, 'window');
             assert_equals(attribution.containerId, '');
             assert_equals(attribution.containerName, '');
             assert_equals(attribution.containerSrc, '');
diff --git a/testing/web-platform/tests/longtask-timing/longtask-in-parentiframe.html b/testing/web-platform/tests/longtask-timing/longtask-in-parentiframe.html
index 778edc1000..7fd5fb672b 100644
--- a/testing/web-platform/tests/longtask-timing/longtask-in-parentiframe.html
+++ b/testing/web-platform/tests/longtask-timing/longtask-in-parentiframe.html
@@ -8,14 +8,12 @@
 
 <script>
   const t = async_test(t => {
-    if (typeof PerformanceLongTaskTiming === 'undefined') {
-        assert_unreached("Longtasks are not supported.");
-        t.done();
-    }
+    assert_implements(window.PerformanceLongTaskTiming, 'Longtasks are not supported.');
     window.addEventListener('message', t.step_func(e => {
       assert_equals(e.data['entryType'], 'longtask');
       assert_equals(e.data['frame-attribution'], 'same-origin-ancestor');
       assert_equals(e.data['task-attribution'], 'unknown');
+      assert_equals(e.data['containerType'], 'window');
       assert_equals(e.data['containerId'], '');
       assert_equals(e.data['containerName'], '');
       assert_equals(e.data['containerSrc'], '');
diff --git a/testing/web-platform/tests/longtask-timing/longtask-in-raf.html b/testing/web-platform/tests/longtask-timing/longtask-in-raf.html
index 2d30ac36b9..40508e1e67 100644
--- a/testing/web-platform/tests/longtask-timing/longtask-in-raf.html
+++ b/testing/web-platform/tests/longtask-timing/longtask-in-raf.html
@@ -10,10 +10,7 @@
 <div id="log"></div>
 <script>
   async_test(function (t) {
-    if (typeof PerformanceLongTaskTiming === 'undefined') {
-        assert_unreached("Longtasks are not supported.");
-        t.done();
-    }
+    assert_implements(window.PerformanceLongTaskTiming, 'Longtasks are not supported.');
     const observer = new PerformanceObserver(
         t.step_func(function (entryList) {
             const entries = entryList.getEntries();
@@ -32,6 +29,7 @@
             assert_equals(attribution.name, 'unknown');
             assert_equals(attribution.duration, 0);
             assert_equals(attribution.startTime, 0);
+            assert_equals(attribution.containerType, 'window');
             assert_equals(attribution.containerId, '');
             assert_equals(attribution.containerName, '');
             assert_equals(attribution.containerSrc, '');
diff --git a/testing/web-platform/tests/longtask-timing/longtask-in-sibling-iframe-crossorigin.html b/testing/web-platform/tests/longtask-timing/longtask-in-sibling-iframe-crossorigin.html
index b73112e3ab..d66fe0c63b 100644
--- a/testing/web-platform/tests/longtask-timing/longtask-in-sibling-iframe-crossorigin.html
+++ b/testing/web-platform/tests/longtask-timing/longtask-in-sibling-iframe-crossorigin.html
@@ -8,14 +8,12 @@
 
 <script>
   async_test(t => {
-    if (typeof PerformanceLongTaskTiming === 'undefined') {
-        assert_unreached("Longtasks are not supported.");
-        t.done();
-    }
+    assert_implements(window.PerformanceLongTaskTiming, 'Longtasks are not supported.');
     window.addEventListener('message', t.step_func(e => {
       assert_equals(e.data['entryType'], 'longtask');
       assert_equals(e.data['frame-attribution'], 'cross-origin-unreachable');
       assert_equals(e.data['task-attribution'], 'unknown');
+      assert_equals(e.data['containerType'], 'window');
       assert_equals(e.data['containerId'], '');
       assert_equals(e.data['containerName'], '');
       assert_equals(e.data['containerSrc'], '');
diff --git a/testing/web-platform/tests/longtask-timing/longtask-in-sibling-iframe.html b/testing/web-platform/tests/longtask-timing/longtask-in-sibling-iframe.html
index 16f0998c22..396a9beeea 100644
--- a/testing/web-platform/tests/longtask-timing/longtask-in-sibling-iframe.html
+++ b/testing/web-platform/tests/longtask-timing/longtask-in-sibling-iframe.html
@@ -8,10 +8,7 @@
 
 <script>
   async_test(t => {
-    if (typeof PerformanceLongTaskTiming === 'undefined') {
-        assert_unreached("Longtasks are not supported.");
-        t.done();
-    }
+    assert_implements(window.PerformanceLongTaskTiming, 'Longtasks are not supported.');
     window.addEventListener('message', t.step_func(e => {
       assert_equals(e.data['entryType'], 'longtask');
       // Ignore any long task that may be produced by the top-level frame.
@@ -20,6 +17,7 @@
 
       assert_equals(e.data['frame-attribution'], 'same-origin');
       assert_equals(e.data['task-attribution'], 'unknown');
+      assert_equals(e.data['containerType'], 'iframe');
       assert_equals(e.data['containerId'], 'longtask-iframe-id');
       assert_equals(e.data['containerName'], 'longtask-iframe-name');
       assert_equals(e.data['containerSrc'], 'resources/subframe-with-longtask.html');
diff --git a/testing/web-platform/tests/longtask-timing/longtask-tojson.html b/testing/web-platform/tests/longtask-timing/longtask-tojson.html
index 20a97a16b0..b1f9b3c9b1 100644
--- a/testing/web-platform/tests/longtask-timing/longtask-tojson.html
+++ b/testing/web-platform/tests/longtask-timing/longtask-tojson.html
@@ -7,10 +7,7 @@
 <body>
 <script>
   async_test(function (t) {
-    if (typeof PerformanceLongTaskTiming === 'undefined') {
-        assert_unreached("Longtasks are not supported.");
-        t.done();
-    }
+    assert_implements(window.PerformanceLongTaskTiming, 'Longtasks are not supported.');
     const observer = new PerformanceObserver(
       t.step_func(function (entryList) {
         const entries = entryList.getEntries();
@@ -74,4 +71,4 @@
   }, 'Test toJSON() in PerformanceLongTaskTiming and TaskAttributionTiming');
 </script>
 </body>
-</html>
\ No newline at end of file
+</html>
diff --git a/testing/web-platform/tests/longtask-timing/resources/subframe-observing-longtask.html b/testing/web-platform/tests/longtask-timing/resources/subframe-observing-longtask.html
index b232ecdd47..125ff1e4cb 100644
--- a/testing/web-platform/tests/longtask-timing/resources/subframe-observing-longtask.html
+++ b/testing/web-platform/tests/longtask-timing/resources/subframe-observing-longtask.html
@@ -19,6 +19,7 @@
           'entryType': longtask.entryType,
           'frame-attribution': longtask.name,
           'task-attribution': attribution.name,
+          'containerType': attribution.containerType,
           'containerId': attribution.containerId,
           'containerName': attribution.containerName,
           'containerSrc': attribution.containerSrc
diff --git a/testing/web-platform/tests/longtask-timing/shared-renderer/longtask-in-new-window.html b/testing/web-platform/tests/longtask-timing/shared-renderer/longtask-in-new-window.html
index 3a68d1451a..7668d995d8 100644
--- a/testing/web-platform/tests/longtask-timing/shared-renderer/longtask-in-new-window.html
+++ b/testing/web-platform/tests/longtask-timing/shared-renderer/longtask-in-new-window.html
@@ -11,10 +11,7 @@
   This window opens a new window which contains a longtask. We test that the
   longtask from the new window is not observed by the observer of this window. */
 async_test(t => {
-  if (typeof PerformanceLongTaskTiming === 'undefined') {
-      assert_unreached("Longtasks are not supported.");
-      t.done();
-  }
+  assert_implements(window.PerformanceLongTaskTiming, 'Longtasks are not supported.');
   const observer = new PerformanceObserver(
       t.step_func(function (entryList) {
           const entries = entryList.getEntries();
diff --git a/testing/web-platform/tests/longtask-timing/supported-longtask-types.window.js b/testing/web-platform/tests/longtask-timing/supported-longtask-types.window.js
index 3c68c01d32..efb393ad84 100644
--- a/testing/web-platform/tests/longtask-timing/supported-longtask-types.window.js
+++ b/testing/web-platform/tests/longtask-timing/supported-longtask-types.window.js
@@ -1,6 +1,5 @@
 test(() => {
-  if (typeof PerformanceObserver.supportedEntryTypes === "undefined")
-    assert_unreached("supportedEntryTypes is not supported.");
+  assert_implements(typeof PerformanceObserver.supportedEntryTypes !== "undefined", 'supportedEntryTypes is not supported');
   const types = PerformanceObserver.supportedEntryTypes;
   assert_true(types.includes("longtask"),
     "There should be 'longtask' in PerformanceObserver.supportedEntryTypes");
@@ -20,19 +19,17 @@ function syncWait(waitDuration) {
   return syncWait(waitDuration - (performance.now() - startTime));
 }
 
-if (typeof PerformanceObserver.supportedEntryTypes !== "undefined") {
-  const entryType = "longtask";
-  if (PerformanceObserver.supportedEntryTypes.includes(entryType)) {
-    promise_test(async () => {
-      await new Promise((resolve) => {
-        new PerformanceObserver(function (list, observer) {
-          observer.disconnect();
-          resolve();
-        }).observe({entryTypes: [entryType]});
+const entryType = "longtask";
+promise_test(async () => {
+  assert_implements(typeof PerformanceObserver.supportedEntryTypes !== "undefined", 'supportedEntryTypes is not supported');
+  assert_implements(typeof PerformanceObserver.supportedEntryTypes.includes(entryType), `supportedEntryTypes does not include '${entryType}'`);
+  await new Promise((resolve) => {
+    new PerformanceObserver(function (list, observer) {
+      observer.disconnect();
+      resolve();
+    }).observe({entryTypes: [entryType]});
 
-        // Force the PerformanceEntry.
-        syncWait(50);
-      })
-    }, `'${entryType}' entries should be observable.`)
-  }
-}
+    // Force the PerformanceEntry.
+    syncWait(50);
+  })
+}, `'${entryType}' entries should be observable.`)
diff --git a/testing/web-platform/tests/mathml/presentation-markup/direction/direction-006-ref.html b/testing/web-platform/tests/mathml/presentation-markup/direction/direction-006-ref.html
new file mode 100644
index 0000000000..39e6dabdfb
--- /dev/null
+++ b/testing/web-platform/tests/mathml/presentation-markup/direction/direction-006-ref.html
@@ -0,0 +1,74 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <meta charset="utf-8"/>
+    <title>RTL mtable and mtable with frame</title>
+    <link rel="stylesheet" type="text/css" href="/fonts/ahem.css" />
+    <style>
+      math, math * {
+          font: 25px Ahem;
+      }
+    </style>
+  </head>
+  <body>
+
+    <p>
+      <math>
+        <mtable>
+          <mtr>
+            <mtd>
+              <mtext>É</mtext>
+            </mtd>
+            <mtd>
+              <mtext>p</mtext>
+            </mtd>
+            <mtd>
+              <mtext>X</mtext>
+            </mtd>
+          </mtr>
+          <mtr>
+            <mtd>
+              <mtext>pÉ</mtext>
+            </mtd>
+            <mtd>
+              <mtext>XÉ</mtext>
+            </mtd>
+            <mtd>
+              <mtext>Xp</mtext>
+            </mtd>
+          </mtr>
+        </mtable>
+      </math>
+    </p>
+
+    <p>
+      <math>
+        <mtable frame="solid">
+          <mtr>
+            <mtd>
+              <mtext>É</mtext>
+            </mtd>
+            <mtd>
+              <mtext>p</mtext>
+            </mtd>
+            <mtd>
+              <mtext>X</mtext>
+            </mtd>
+          </mtr>
+          <mtr>
+            <mtd>
+              <mtext>pÉ</mtext>
+            </mtd>
+            <mtd>
+              <mtext>XÉ</mtext>
+            </mtd>
+            <mtd>
+              <mtext>Xp</mtext>
+            </mtd>
+          </mtr>
+        </mtable>
+      </math>
+    </p>
+
+  </body>
+</html>
diff --git a/testing/web-platform/tests/mathml/presentation-markup/direction/direction-006.html b/testing/web-platform/tests/mathml/presentation-markup/direction/direction-006.html
new file mode 100644
index 0000000000..904e7d3fed
--- /dev/null
+++ b/testing/web-platform/tests/mathml/presentation-markup/direction/direction-006.html
@@ -0,0 +1,79 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <meta charset="utf-8"/>
+    <title>RTL mtable and mtable with frame</title>
+    <link rel="help" href="https://mathml-refresh.github.io/mathml-core/#attributes-common-to-html-and-mathml-elements">
+    <link rel="help" href="https://mathml-refresh.github.io/mathml-core/#css-styling">
+    <link rel="help" href="https://mathml-refresh.github.io/mathml-core/#tabular-math">
+    <meta name="assert" content="Verify RTL math table renders the same as the column mirrored.">
+    <link rel="match" href="direction-006-ref.html">
+    <link rel="stylesheet" type="text/css" href="/fonts/ahem.css" />
+    <style>
+      math, math * {
+          font: 25px Ahem;
+      }
+    </style>
+  </head>
+  <body>
+
+    <p>
+      <math dir="rtl">
+        <mtable>
+          <mtr>
+            <mtd>
+              <mtext>X</mtext>
+            </mtd>
+            <mtd>
+              <mtext>p</mtext>
+            </mtd>
+            <mtd>
+              <mtext>É</mtext>
+            </mtd>
+          </mtr>
+          <mtr>
+            <mtd>
+              <mtext>Xp</mtext>
+            </mtd>
+            <mtd>
+              <mtext>XÉ</mtext>
+            </mtd>
+            <mtd>
+              <mtext>pÉ</mtext>
+            </mtd>
+          </mtr>
+        </mtable>
+      </math>
+    </p>
+
+    <p>
+      <math dir="rtl">
+        <mtable frame="solid">
+          <mtr>
+            <mtd>
+              <mtext>X</mtext>
+            </mtd>
+            <mtd>
+              <mtext>p</mtext>
+            </mtd>
+            <mtd>
+              <mtext>É</mtext>
+            </mtd>
+          </mtr>
+          <mtr>
+            <mtd>
+              <mtext>Xp</mtext>
+            </mtd>
+            <mtd>
+              <mtext>XÉ</mtext>
+            </mtd>
+            <mtd>
+              <mtext>pÉ</mtext>
+            </mtd>
+          </mtr>
+        </mtable>
+      </math>
+    </p>
+
+  </body>
+</html>
diff --git a/testing/web-platform/tests/mathml/presentation-markup/direction/direction-007-ref.html b/testing/web-platform/tests/mathml/presentation-markup/direction/direction-007-ref.html
new file mode 100644
index 0000000000..5c77395f20
--- /dev/null
+++ b/testing/web-platform/tests/mathml/presentation-markup/direction/direction-007-ref.html
@@ -0,0 +1,42 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <meta charset="utf-8"/>
+    <title>mo and embellished mrow/munderover (lspace=1em rspace=2em)</title>
+    <link rel="stylesheet" type="text/css" href="/fonts/ahem.css" />
+    <style>
+      math, math * {
+          font: 25px/1 Ahem;
+      }
+    </style>
+  </head>
+  <body>
+
+    <p>
+      <math>
+        <mtext>p</mtext><mo lspace="2em" rspace="1em">X</mo><mtext>p</mtext>
+      </math>
+    </p>
+
+    <p>
+      <math>
+        <mtext>p</mtext>
+        <mrow><mo lspace="2em" rspace="1em">X</mo></mrow>
+        <mtext>p</mtext>
+      </math>
+    </p>
+
+    <p>
+      <math>
+        <mtext>p</mtext>
+        <munderover>
+          <mo lspace="2em" rspace="1em">X</mo>
+          <mtext>É</mtext>
+          <mtext>É</mtext>
+        </munderover>
+        <mtext>p</mtext>
+      </math>
+    </p>
+
+  </body>
+</html>
diff --git a/testing/web-platform/tests/mathml/presentation-markup/direction/direction-007.html b/testing/web-platform/tests/mathml/presentation-markup/direction/direction-007.html
new file mode 100644
index 0000000000..7137e2640f
--- /dev/null
+++ b/testing/web-platform/tests/mathml/presentation-markup/direction/direction-007.html
@@ -0,0 +1,50 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <meta charset="utf-8"/>
+    <title>mo and embellished mrow/munderover (lspace=1em rspace=2em)</title>
+    <link rel="help" href="https://mathml-refresh.github.io/mathml-core/#attributes-common-to-html-and-mathml-elements">
+    <link rel="help" href="https://mathml-refresh.github.io/mathml-core/#css-styling">
+    <link rel="help" href="https://mathml-refresh.github.io/mathml-core/#embellished-operators">
+    <link rel="help" href="https://mathml-refresh.github.io/mathml-core/#operator-fence-separator-or-accent-mo">
+    <link rel="help" href="https://mathml-refresh.github.io/mathml-core/#horizontally-group-sub-expressions-mrow">
+    <link rel="help" href="https://mathml-refresh.github.io/mathml-core/#underscripts-and-overscripts-munder-mover-munderover">
+    <meta name="assert" content="Verify that the lspace/rspace on an mo or an embellished mrow/munderover element are switched in RTL mode">
+    <link rel="match" href="direction-007-ref.html">
+    <link rel="stylesheet" type="text/css" href="/fonts/ahem.css" />
+    <style>
+      math, math * {
+          font: 25px/1 Ahem;
+      }
+    </style>
+  </head>
+  <body>
+
+    <p>
+      <math dir="rtl">
+        <mtext>p</mtext><mo lspace="1em" rspace="2em">X</mo><mtext>p</mtext>
+      </math>
+    </p>
+
+    <p>
+      <math dir="rtl">
+        <mtext>p</mtext>
+        <mrow><mo lspace="1em" rspace="2em">X</mo></mrow>
+        <mtext>p</mtext>
+      </math>
+    </p>
+
+    <p>
+      <math dir="rtl">
+        <mtext>p</mtext>
+        <munderover>
+          <mo lspace="1em" rspace="2em">X</mo>
+          <mtext>É</mtext>
+          <mtext>É</mtext>
+        </munderover>
+        <mtext>p</mtext>
+      </math>
+    </p>
+
+  </body>
+</html>
diff --git a/testing/web-platform/tests/mathml/presentation-markup/direction/direction-008-ref.html b/testing/web-platform/tests/mathml/presentation-markup/direction/direction-008-ref.html
new file mode 100644
index 0000000000..492fa9539a
--- /dev/null
+++ b/testing/web-platform/tests/mathml/presentation-markup/direction/direction-008-ref.html
@@ -0,0 +1,27 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <meta charset="utf-8"/>
+    <title>embellished mfrac (lspace=1em rspace=2em)</title>
+    <link rel="stylesheet" type="text/css" href="/fonts/ahem.css" />
+    <style>
+      math, math * {
+          font: 25px/1 Ahem;
+      }
+    </style>
+  </head>
+  <body>
+
+    <p>
+      <math>
+        <mtext>p</mtext>
+        <mfrac>
+          <mo lspace="2em" rspace="1em">X</mo>
+          <mtext>É</mtext>
+        </mfrac>
+        <mtext>p</mtext>
+      </math>
+    </p>
+
+  </body>
+</html>
diff --git a/testing/web-platform/tests/mathml/presentation-markup/direction/direction-008.html b/testing/web-platform/tests/mathml/presentation-markup/direction/direction-008.html
new file mode 100644
index 0000000000..5c98b07410
--- /dev/null
+++ b/testing/web-platform/tests/mathml/presentation-markup/direction/direction-008.html
@@ -0,0 +1,33 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <meta charset="utf-8"/>
+    <title>embellished mfrac (lspace=1em rspace=2em)</title>
+    <link rel="help" href="https://mathml-refresh.github.io/mathml-core/#attributes-common-to-html-and-mathml-elements">
+    <link rel="help" href="https://mathml-refresh.github.io/mathml-core/#css-styling">
+    <link rel="help" href="https://mathml-refresh.github.io/mathml-core/#fractions-mfrac">
+    <link rel="help" href="https://mathml-refresh.github.io/mathml-core/#embellished-operators">
+    <meta name="assert" content="Verify that the lspace/rspace on an embellished mfrac element are switched in RTL mode">
+    <link rel="match" href="direction-008-ref.html">
+    <link rel="stylesheet" type="text/css" href="/fonts/ahem.css" />
+    <style>
+      math, math * {
+          font: 25px/1 Ahem;
+      }
+    </style>
+  </head>
+  <body>
+
+    <p>
+      <math dir="rtl">
+        <mtext>p</mtext>
+        <mfrac>
+          <mo lspace="1em" rspace="2em">X</mo>
+          <mtext>É</mtext>
+        </mfrac>
+        <mtext>p</mtext>
+      </math>
+    </p>
+
+  </body>
+</html>
diff --git a/testing/web-platform/tests/mathml/presentation-markup/direction/direction-009-ref.html b/testing/web-platform/tests/mathml/presentation-markup/direction/direction-009-ref.html
new file mode 100644
index 0000000000..7ed4796814
--- /dev/null
+++ b/testing/web-platform/tests/mathml/presentation-markup/direction/direction-009-ref.html
@@ -0,0 +1,21 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <meta charset="utf-8"/>
+    <title>RTL ms lquote="X" rquote="p"</title>
+    <style>
+      math {
+          font: 25px/1 Ahem;
+      }
+    </style>
+  </head>
+  <body>
+
+    <p>
+      <math>
+        <ms lquote="p" rquote="X">É</ms>
+      </math>
+    </p>
+
+  </body>
+</html>
diff --git a/testing/web-platform/tests/mathml/presentation-markup/direction/direction-009.html b/testing/web-platform/tests/mathml/presentation-markup/direction/direction-009.html
new file mode 100644
index 0000000000..bf8caf16ae
--- /dev/null
+++ b/testing/web-platform/tests/mathml/presentation-markup/direction/direction-009.html
@@ -0,0 +1,27 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <meta charset="utf-8"/>
+    <title>RTL ms lquote="X" rquote="p"</title>
+    <link rel="help" href="https://mathml-refresh.github.io/mathml-core/#attributes-common-to-html-and-mathml-elements">
+    <link rel="help" href="https://mathml-refresh.github.io/mathml-core/#css-styling">
+    <link rel="help" href="https://mathml-refresh.github.io/mathml-core/#string-literal-ms">
+    <meta name="assert" content="Verify that a RTL ms element renders the same as if its left and right quotes were switched.">
+    <link rel="match" href="direction-009-ref.html">
+    <link rel="stylesheet" type="text/css" href="/fonts/ahem.css" />
+    <style>
+      math {
+          font: 25px/1 Ahem;
+      }
+    </style>
+  </head>
+  <body>
+
+    <p>
+      <math dir="rtl">
+        <ms lquote="X" rquote="p">É</ms>
+      </math>
+    </p>
+
+  </body>
+</html>
diff --git a/testing/web-platform/tests/mathml/presentation-markup/direction/direction-010-ref.html b/testing/web-platform/tests/mathml/presentation-markup/direction/direction-010-ref.html
new file mode 100644
index 0000000000..4f595ed49f
--- /dev/null
+++ b/testing/web-platform/tests/mathml/presentation-markup/direction/direction-010-ref.html
@@ -0,0 +1,44 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <meta charset="utf-8"/>
+    <title>dir="rtl" VS direction: rtl on math/mrow/mstyle</title>
+    <link rel="stylesheet" type="text/css" href="/fonts/ahem.css" />
+    <style>
+      math {
+          font: 25px/1 Ahem;
+      }
+    </style>
+  </head>
+  <body>
+
+    <p>
+      <math style="direction: rtl">
+        <mtext>X</mtext>
+        <mtext>p</mtext>
+        <mtext>É</mtext>
+      </math>
+    </p>
+
+    <p>
+      <math>
+        <mrow style="direction: rtl">
+          <mtext>X</mtext>
+          <mtext>p</mtext>
+          <mtext>É</mtext>
+        </mrow>
+      </math>
+    </p>
+
+    <p>
+      <math>
+        <mstyle mathcolor="blue" style="direction: rtl">
+          <mtext>X</mtext>
+          <mtext>p</mtext>
+          <mtext>É</mtext>
+        </mstyle>
+      </math>
+    </p>
+
+  </body>
+</html>
diff --git a/testing/web-platform/tests/mathml/presentation-markup/direction/direction-010.html b/testing/web-platform/tests/mathml/presentation-markup/direction/direction-010.html
new file mode 100644
index 0000000000..6dc095ac1f
--- /dev/null
+++ b/testing/web-platform/tests/mathml/presentation-markup/direction/direction-010.html
@@ -0,0 +1,51 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <meta charset="utf-8"/>
+    <title>dir="rtl" VS direction: rtl on math/mrow/mstyle</title>
+    <link rel="help" href="https://mathml-refresh.github.io/mathml-core/#attributes-common-to-html-and-mathml-elements">
+    <link rel="help" href="https://mathml-refresh.github.io/mathml-core/#css-styling">
+    <link rel="help" href="https://mathml-refresh.github.io/mathml-core/#horizontally-group-sub-expressions-mrow">
+    <link rel="help" href="https://mathml-refresh.github.io/mathml-core/#style-change-mstyle">
+    <link rel="help" href="https://mathml-refresh.github.io/mathml-core/#the-top-level-math-element">
+    <meta name="assert" content="Verify that math, mrow and mstyle with a dir=rtl attribute render the same as CSS direction right-to-left.">
+    <link rel="match" href="direction-010-ref.html">
+    <link rel="stylesheet" type="text/css" href="/fonts/ahem.css" />
+    <style>
+      math {
+          font: 25px/1 Ahem;
+      }
+    </style>
+  </head>
+  <body>
+
+    <p>
+      <math dir="rtl">
+        <mtext>X</mtext>
+        <mtext>p</mtext>
+        <mtext>É</mtext>
+      </math>
+    </p>
+
+    <p>
+      <math>
+        <mrow dir="rtl">
+          <mtext>X</mtext>
+          <mtext>p</mtext>
+          <mtext>É</mtext>
+        </mrow>
+      </math>
+    </p>
+
+    <p>
+      <math>
+        <mstyle mathcolor="blue" dir="rtl">
+          <mtext>X</mtext>
+          <mtext>p</mtext>
+          <mtext>É</mtext>
+        </mstyle>
+      </math>
+    </p>
+
+  </body>
+</html>
diff --git a/testing/web-platform/tests/mathml/presentation-markup/fractions/frac-linethickness-002-ref.html b/testing/web-platform/tests/mathml/presentation-markup/fractions/frac-linethickness-002-ref.html
index 69663938c1..bf1938bd28 100644
--- a/testing/web-platform/tests/mathml/presentation-markup/fractions/frac-linethickness-002-ref.html
+++ b/testing/web-platform/tests/mathml/presentation-markup/fractions/frac-linethickness-002-ref.html
@@ -30,8 +30,8 @@
         <mspace width="20px" height="10px" style="background: cyan"></mspace>
       </mfrac>
     </math>
-    <math style="font-size: 180px">
-      <mfrac linethickness="0.3888888888888889em">
+    <math>
+      <mfrac>
         <mspace width="20px" height="70px" style="background: blue"></mspace>
         <mspace width="20px" height="10px" style="background: cyan"></mspace>
       </mfrac>
diff --git a/testing/web-platform/tests/mathml/presentation-markup/fractions/frac-linethickness-002.html b/testing/web-platform/tests/mathml/presentation-markup/fractions/frac-linethickness-002.html
index fd45994646..deb8fd3eb7 100644
--- a/testing/web-platform/tests/mathml/presentation-markup/fractions/frac-linethickness-002.html
+++ b/testing/web-platform/tests/mathml/presentation-markup/fractions/frac-linethickness-002.html
@@ -33,7 +33,8 @@
         <mspace width="20px" height="10px" style="background: cyan"></mspace>
       </mfrac>
     </math>
-    <math style="font-size: 180px">
+    <math>
+      <!-- Namedspace values are invalid in MathML Core. -->
       <mfrac linethickness="veryverythickmathspace">
         <mspace width="20px" height="70px" style="background: blue"></mspace>
         <mspace width="20px" height="10px" style="background: cyan"></mspace>
diff --git a/testing/web-platform/tests/mathml/relations/css-styling/attribute-mapping-001.html b/testing/web-platform/tests/mathml/relations/css-styling/attribute-mapping-001.html
new file mode 100644
index 0000000000..c7afa7a112
--- /dev/null
+++ b/testing/web-platform/tests/mathml/relations/css-styling/attribute-mapping-001.html
@@ -0,0 +1,85 @@
+<!DOCTYPE html>
+<html>
+<head>
+<meta charset="utf-8">
+<title>Attribute mapping</title>
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#legacy-mathml-style-attributes">
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#attributes-common-to-html-and-mathml-elements">
+<meta name="assert" content="Verify that dir, mathcolor, mathbackground and mathsize are mapped to CSS">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/mathml/support/mathml-fragments.js"></script>
+<style>
+  #container {
+      color: blue;
+      font-size: 50px;
+  }
+</style>
+<script>
+  setup({ explicit_done: true });
+  window.addEventListener("load", runTests);
+  function runTests() {
+      var container = document.getElementById("container");
+      for (tag in MathMLFragments) {
+          container.insertAdjacentHTML("beforeend", `<math>${MathMLFragments[tag]}</math>`);
+      }
+      Array.from(document.getElementsByClassName("element")).forEach(element => {
+          var tag = element.tagName;
+          var style = window.getComputedStyle(element);
+
+          test(function() {
+              assert_equals(style.getPropertyValue("direction"), "ltr", "no attribute");
+              element.setAttribute("dir", "rtl");
+              assert_equals(style.getPropertyValue("direction"), "rtl", "attribute specified");
+              element.setAttribute("dir", "RtL");
+              assert_equals(style.getPropertyValue("direction"), "rtl", "case insensitive");
+          }, `dir on the ${tag} element is mapped to CSS direction`)
+
+          test(function() {
+              assert_equals(style.getPropertyValue("color"),
+                            tag === "merror" ?
+                            "rgb(255, 0, 0)" : "rgb(0, 0, 255)",
+                            "no attribute");
+              element.setAttribute("mathcolor", "black");
+              assert_equals(style.getPropertyValue("color"), "rgb(0, 0, 0)", "attribute specified");
+              // The color names are case-insensitive.
+              // See https://www.w3.org/TR/css-color-3/#html4
+              element.setAttribute("mathcolor", "GrEeN");
+              assert_equals(style.getPropertyValue("color"), "rgb(0, 128, 0)", "case insensitive");
+          }, `mathcolor on the ${tag} element is mapped to CSS color`);
+
+          test(function() {
+              assert_equals(style.getPropertyValue("background-color"),
+                            tag === "merror" ?
+                            "rgb(255, 255, 224)" : "rgba(0, 0, 0, 0)",
+                            "no attribute");
+              element.setAttribute("mathbackground", "lightblue");
+              assert_equals(style.getPropertyValue("background-color"), "rgb(173, 216, 230)", "attribute specified");
+              // The color names are case-insensitive.
+              // See https://www.w3.org/TR/css-color-3/#html4
+              element.setAttribute("mathbackground", "YeLlOw");
+              assert_equals(style.getPropertyValue("background-color"), "rgb(255, 255, 0)", "case insensitive");
+          }, `mathbackground on the ${tag} element is mapped to CSS background-color`);
+
+          test(function() {
+              assert_equals(style.getPropertyValue("font-size"), "50px", "no attribute");
+              element.setAttribute("mathsize", "20px");
+              assert_equals(style.getPropertyValue("font-size"), "20px", "attribute specified");
+              // unit identifiers are ASCII case-insensitive.
+              // https://www.w3.org/TR/css-values-3/#typedef-dimension
+              element.setAttribute("mathsize", "30Px");
+              assert_equals(style.getPropertyValue("font-size"), "30px", "case insensitive");
+          }, `mathsize on the ${tag} element is mapped to CSS font-size`);
+      });
+
+      done();
+  }
+</script>
+</head>
+<body>
+  <div id="log"></div>
+  <div id="container">
+    <math class="element"></math>
+  </div>
+</body>
+</html>
diff --git a/testing/web-platform/tests/mathml/relations/css-styling/attribute-mapping-002.html b/testing/web-platform/tests/mathml/relations/css-styling/attribute-mapping-002.html
new file mode 100644
index 0000000000..329578dc95
--- /dev/null
+++ b/testing/web-platform/tests/mathml/relations/css-styling/attribute-mapping-002.html
@@ -0,0 +1,59 @@
+<!DOCTYPE html>
+<html>
+<head>
+<meta charset="utf-8">
+<title>Attribute mapping</title>
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#the-mathvariant-attribute">
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#the-displaystyle-and-scriptlevel-attributes">
+<meta name="assert" content="Verify that mathvariant, scriptlevel, displaystyle are mapped to CSS">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/mathml/support/mathml-fragments.js"></script>
+<script>
+  setup({ explicit_done: true });
+  window.addEventListener("load", runTests);
+  function runTests() {
+      var container = document.getElementById("container");
+      for (tag in MathMLFragments) {
+          container.insertAdjacentHTML("beforeend", `<math>${MathMLFragments[tag]}</math>`);
+      }
+      Array.from(document.getElementsByClassName("element")).forEach(element => {
+          var tag = element.tagName;
+          var style = window.getComputedStyle(element);
+
+          test(function() {
+              assert_equals(style.getPropertyValue("text-transform"),
+                            tag === "mi" ? "math-auto" : "none",
+                            "no attribute");
+              element.setAttribute("mathvariant", "fraktur");
+              assert_equals(style.getPropertyValue("text-transform"), "math-fraktur", "attribute specified");
+              element.setAttribute("mathvariant", "DoUbLe-StRuCk");
+              assert_equals(style.getPropertyValue("text-transform"), "math-double-struck", "case insensitive");
+          }, `mathvariant on the ${tag} element is mapped to CSS text-transform`)
+
+          test(function() {
+              assert_equals(style.getPropertyValue("math-script-level"), "0", "no attribute");
+              element.setAttribute("scriptlevel", "10");
+              assert_equals(style.getPropertyValue("math-script-level"), "10", "attribute specified");
+          }, `scriptlevel on the ${tag} element is mapped to CSS math-script-level`);
+
+          test(function() {
+              assert_equals(style.getPropertyValue("math-style"), "inline", "no attribute");
+              element.setAttribute("displaystyle", "true");
+              assert_equals(style.getPropertyValue("math-style"), "display", "attribute specified");
+              element.setAttribute("displaystyle", "TrUe");
+              assert_equals(style.getPropertyValue("math-style"), "display", "case insensitive");
+          }, `displaystyle on the ${tag} element is mapped to CSS math-style`);
+      });
+
+      done();
+  }
+</script>
+</head>
+<body>
+  <div id="log"></div>
+  <div id="container">
+    <math class="element"></math>
+  </div>
+</body>
+</html>
diff --git a/testing/web-platform/tests/mathml/relations/css-styling/lengths-2-ref.html b/testing/web-platform/tests/mathml/relations/css-styling/lengths-2-ref.html
deleted file mode 100644
index 9fca6f4963..0000000000
--- a/testing/web-platform/tests/mathml/relations/css-styling/lengths-2-ref.html
+++ /dev/null
@@ -1,14 +0,0 @@
-<!DOCTYPE html>
-<html>
-<head>
-<meta charset="utf-8"/>
-<title>MathML lengths (reference)</title>
-</head>
-<body>
-  <p>Test passes if there is a green square and no red.</p>
-  <div>
-    <div id="red" style="position: absolute; width: 200px; height: 200px; background: green;">
-    </div>
-  </div>
-</body>
-</html>
diff --git a/testing/web-platform/tests/mathml/relations/css-styling/lengths-2.html b/testing/web-platform/tests/mathml/relations/css-styling/lengths-2.html
index 37cc640b30..b4c982bcfd 100644
--- a/testing/web-platform/tests/mathml/relations/css-styling/lengths-2.html
+++ b/testing/web-platform/tests/mathml/relations/css-styling/lengths-2.html
@@ -1,122 +1,255 @@
 <!DOCTYPE html>
 <html>
 <head>
-<meta charset="utf-8"/>
+<meta charset="utf-8">
 <title>MathML lengths</title>
 <link rel="help" href="https://mathml-refresh.github.io/mathml-core/#cssstyling"/>
-<link rel="match" href="lengths-2-ref.html"/>
-<meta name="assert" content="Verify whether the different namedspaces are accepted for MathML lengths.">
+<meta name="assert" content="Verify various cases of the MathML length syntax.">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
 <style>
   @font-face {
     font-family: TestFont;
     src: url("/fonts/math/xheight500.woff");
   }
-  mpadded {
+  math {
     font-family: TestFont;
-    font-size: 200px; /* 1em = 200px */
-  }
-  div {
-    position: absolute;
-  }
-  #red mspace {
-    background: red;
-  }
-  #green mspace {
-    background: green;
+    font-size: 10px;
   }
 </style>
+<script>
+  var epsilon = .5;
+
+  function getBox(aId) {
+    return document.getElementById(aId).getBoundingClientRect();
+  }
+
+  setup({ explicit_done: true });
+  window.addEventListener("load", function() {
+    // Delay the check to workaround WebKit's bug https://webkit.org/b/174030.
+    requestAnimationFrame(() => { document.fonts.ready.then(runTests); });
+  });
+
+  function runTests() {
+    test(function() {
+      assert_equals(getBox("unitCm").width, 96, "cm");
+      assert_equals(getBox("unitEm").width, 120, "em");
+      assert_equals(getBox("unitEx").width, 500, "ex");
+      assert_equals(getBox("unitIn").width, 288, "in");
+      assert_equals(getBox("unitMm").width, 576, "mm");
+      assert_equals(getBox("unitPc").width, 96, "pc");
+      assert_equals(getBox("unitPercentage").width, 60, "%");
+      assert_equals(getBox("unitPt").width, 96, "pt");
+      assert_equals(getBox("unitPx").width, 123, "px");
+      assert_equals(getBox("unitNone").width, 150, "Unitless");
+    }, "Units");
+
+    test(function() {
+      assert_equals(getBox("spaceCm").width, 96, "cm");
+      assert_equals(getBox("spaceEm").width, 120, "em");
+      assert_equals(getBox("spaceEx").width, 500, "ex");
+      assert_equals(getBox("spaceIn").width, 288, "in");
+      assert_equals(getBox("spaceMm").width, 576, "mm");
+      assert_equals(getBox("spacePc").width, 96, "pc");
+      assert_equals(getBox("spacePercentage").width, 60, "%");
+      assert_equals(getBox("spacePt").width, 96, "pt");
+      assert_equals(getBox("spacePx").width, 123, "px");
+      assert_equals(getBox("spaceNone").width, 150, "Unitless");
+    }, "Trimming of space");
+
+    test(function() {
+      assert_approx_equals(getBox("n0").width, 0, epsilon, "n0");
+      assert_approx_equals(getBox("n1").width, 90, epsilon, "n1");
+      assert_approx_equals(getBox("n2").width, 8, epsilon, "n2");
+      assert_approx_equals(getBox("n3").width, 70, epsilon, "n3");
+      assert_approx_equals(getBox("n4").width, 650, epsilon, "n4");
+      assert_approx_equals(getBox("n5").width, 4320, epsilon, "n5");
+      assert_approx_equals(getBox("n6").width, 1, epsilon, "n6");
+      assert_approx_equals(getBox("n7").width, 8, epsilon, "n7");
+      assert_approx_equals(getBox("n8").width, 65, epsilon, "n8");
+      assert_approx_equals(getBox("n9").width, 432, epsilon, "n9");
+      assert_approx_equals(getBox("n10").width, 123, epsilon, "n10");
+    }, "Non-negative numbers");
+
+    test(function() {
+      var topRef = getBox("ref").top;
+      assert_approx_equals(getBox("N0").top - topRef, -0, epsilon, "N0");
+      assert_approx_equals(topRef - getBox("N1").top, -90, epsilon, "N1");
+      assert_approx_equals(topRef - getBox("N2").top, -8, epsilon, "N2");
+      assert_approx_equals(topRef - getBox("N3").top, -70, epsilon, "N3");
+      assert_approx_equals(topRef - getBox("N4").top, -650, epsilon, "N4");
+      assert_approx_equals(topRef - getBox("N5").top, -4320, epsilon, "N5");
+      assert_approx_equals(topRef - getBox("N6").top, -1, epsilon, "N6");
+      assert_approx_equals(topRef - getBox("N7").top, -8, epsilon, "N7");
+      assert_approx_equals(topRef - getBox("N8").top, -65, epsilon, "N8");
+      assert_approx_equals(topRef - getBox("N9").top, -432, epsilon, "N9");
+      assert_approx_equals(topRef - getBox("N10").top, -123, epsilon, "N10");
+    }, "Non-positive numbers");
+
+    test(function() {
+      // Namedspace values are invalid in MathML Core.
+      ["veryverythinmathspace",
+       "verythinmathspace",
+       "thinmathspace",
+       "mediummathspace",
+       "thickmathspace",
+       "verythickmathspace",
+       "veryverythickmathspace",
+       "negativeveryverythinmathspace",
+       "negativeverythinmathspace",
+       "negativethinmathspace",
+       "negativemediummathspace",
+       "negativethickmathspace",
+       "negativeverythickmathspace",
+       "negativeveryverythickmathspace"
+      ].forEach(function(space) {
+          var mrow = document.getElementById(space);
+          var boxBefore = mrow.firstElementChild.getBoundingClientRect();
+          var boxAfter = mrow.lastElementChild.getBoundingClientRect();
+          assert_equals(boxAfter.left - boxBefore.right, 0, space);
+      });
+    }, "Legacy namedspaces");
+
+    done();
+  }
+</script>
 </head>
 <body>
-  <p>Test passes if there is a green square and no red.</p>
-  <div>
-    <div id="red" style="position: absolute; width: 200px; height: 200px; background: green;">
-      <!-- veryverythinmathspace -->
-      <div style="left: 0px;"><math><mpadded height="100px" depth="100px" voffset="1veryverythinmathspace"><mspace width="10px" height="10px"/></mpadded></math></div>
-      <div style="left: 10px;"><math><mpadded height="100px" depth="100px" voffset="0.05555555555555556em"><mspace width="10px" height="10px"/></mpadded></math></div>
-      <!-- verythinmathspace -->
-      <div style="left: 20px;"><math><mpadded height="100px" depth="100px" voffset="1verythinmathspace"><mspace width="10px" height="10px"/></mpadded></math></div>
-      <div style="left: 30px;"><math><mpadded height="100px" depth="100px" voffset="0.1111111111111111em"><mspace width="10px" height="10px"/></mpadded></math></div>
-      <!-- thinmathspace -->
-      <div style="left: 40px;"><math><mpadded height="100px" depth="100px" voffset="1thinmathspace"><mspace width="10px" height="10px"/></mpadded></math></div>
-      <div style="left: 50px;"><math><mpadded height="100px" depth="100px" voffset="0.1666666666666667em"><mspace width="10px" height="10px"/></mpadded></math></div>
-      <!-- mediummathspace -->
-      <div style="left: 60px;"><math><mpadded height="100px" depth="100px" voffset="1mediummathspace"><mspace width="10px" height="10px"/></mpadded></math></div>
-      <div style="left: 70px;"><math><mpadded height="100px" depth="100px" voffset="0.2222222222222222em"><mspace width="10px" height="10px"/></mpadded></math></div>
-      <!-- thickmathspace -->
-      <div style="left: 80px;"><math><mpadded height="100px" depth="100px" voffset="1thickmathspace"><mspace width="10px" height="10px"/></mpadded></math></div>
-      <div style="left: 90px;"><math><mpadded height="100px" depth="100px" voffset="0.2777777777777778em"><mspace width="10px" height="10px"/></mpadded></math></div>
-      <!-- verythickmathspace -->
-      <div style="left: 100px;"><math><mpadded height="100px" depth="100px" voffset="1verythickmathspace"><mspace width="10px" height="10px"/></mpadded></math></div>
-      <div style="left: 110px;"><math><mpadded height="100px" depth="100px" voffset="0.3333333333333333em"><mspace width="10px" height="10px"/></mpadded></math></div>
-      <!-- veryverythickmathspace -->
-      <div style="left: 120px;"><math><mpadded height="100px" depth="100px" voffset="1veryverythickmathspace"><mspace width="10px" height="10px"/></mpadded></math></div>
-      <div style="left: 130px;"><math><mpadded height="100px" depth="100px" voffset="0.3888888888888889em"><mspace width="10px" height="10px"/></mpadded></math></div>
-      <!-- negativeveryverythinmathspace -->
-      <div style="left: 0px;"><math><mpadded height="100px" depth="100px" voffset="1negativeveryverythinmathspace"><mspace width="10px" height="10px"/></mpadded></math></div>
-      <div style="left: 10px;"><math><mpadded height="100px" depth="100px" voffset="-0.05555555555555556em"><mspace width="10px" height="10px"/></mpadded></math></div>
-      <!-- negativeverythinmathspace -->
-      <div style="left: 20px;"><math><mpadded height="100px" depth="100px" voffset="1negativeverythinmathspace"><mspace width="10px" height="10px"/></mpadded></math></div>
-      <div style="left: 30px;"><math><mpadded height="100px" depth="100px" voffset="-0.1111111111111111em"><mspace width="10px" height="10px"/></mpadded></math></div>
-      <!-- negativethinmathspace -->
-      <div style="left: 40px;"><math><mpadded height="100px" depth="100px" voffset="1negativethinmathspace"><mspace width="10px" height="10px"/></mpadded></math></div>
-      <div style="left: 50px;"><math><mpadded height="100px" depth="100px" voffset="-0.1666666666666667em"><mspace width="10px" height="10px"/></mpadded></math></div>
-      <!-- negativemediummathspace -->
-      <div style="left: 60px;"><math><mpadded height="100px" depth="100px" voffset="1negativemediummathspace"><mspace width="10px" height="10px"/></mpadded></math></div>
-      <div style="left: 70px;"><math><mpadded height="100px" depth="100px" voffset="-0.2222222222222222em"><mspace width="10px" height="10px"/></mpadded></math></div>
-      <!-- negativethickmathspace -->
-      <div style="left: 80px;"><math><mpadded height="100px" depth="100px" voffset="1negativethickmathspace"><mspace width="10px" height="10px"/></mpadded></math></div>
-      <div style="left: 90px;"><math><mpadded height="100px" depth="100px" voffset="-0.2777777777777778em"><mspace width="10px" height="10px"/></mpadded></math></div>
-      <!-- negativeverythickmathspace -->
-      <div style="left: 100px;"><math><mpadded height="100px" depth="100px" voffset="1negativeverythickmathspace"><mspace width="10px" height="10px"/></mpadded></math></div>
-      <div style="left: 110px;"><math><mpadded height="100px" depth="100px" voffset="-0.3333333333333333em"><mspace width="10px" height="10px"/></mpadded></math></div>
-      <!-- negativeveryverythickmathspace -->
-      <div style="left: 120px;"><math><mpadded height="100px" depth="100px" voffset="1negativeveryverythickmathspace"><mspace width="10px" height="10px"/></mpadded></math></div>
-      <div style="left: 130px;"><math><mpadded height="100px" depth="100px" voffset="-0.3888888888888889em"><mspace width="10px" height="10px"/></mpadded></math></div>
-    </div>
-    <div id="green" style="position: absolute; width: 200px; height: 200px;">
-      <!-- veryverythinmathspace -->
-      <div style="left: 10px;"><math><mpadded height="100px" depth="100px" voffset="1veryverythinmathspace"><mspace width="10px" height="10px"/></mpadded></math></div>
-      <div style="left: 0px;"><math><mpadded height="100px" depth="100px" voffset="0.05555555555555556em"><mspace width="10px" height="10px"/></mpadded></math></div>
-      <!-- verythinmathspace -->
-      <div style="left: 30px;"><math><mpadded height="100px" depth="100px" voffset="1verythinmathspace"><mspace width="10px" height="10px"/></mpadded></math></div>
-      <div style="left: 20px;"><math><mpadded height="100px" depth="100px" voffset="0.1111111111111111em"><mspace width="10px" height="10px"/></mpadded></math></div>
-      <!-- thinmathspace -->
-      <div style="left: 50px;"><math><mpadded height="100px" depth="100px" voffset="1thinmathspace"><mspace width="10px" height="10px"/></mpadded></math></div>
-      <div style="left: 40px;"><math><mpadded height="100px" depth="100px" voffset="0.1666666666666667em"><mspace width="10px" height="10px"/></mpadded></math></div>
-      <!-- mediummathspace -->
-      <div style="left: 70px;"><math><mpadded height="100px" depth="100px" voffset="1mediummathspace"><mspace width="10px" height="10px"/></mpadded></math></div>
-      <div style="left: 60px;"><math><mpadded height="100px" depth="100px" voffset="0.2222222222222222em"><mspace width="10px" height="10px"/></mpadded></math></div>
-      <!-- thickmathspace -->
-      <div style="left: 90px;"><math><mpadded height="100px" depth="100px" voffset="1thickmathspace"><mspace width="10px" height="10px"/></mpadded></math></div>
-      <div style="left: 80px;"><math><mpadded height="100px" depth="100px" voffset="0.2777777777777778em"><mspace width="10px" height="10px"/></mpadded></math></div>
-      <!-- verythickmathspace -->
-      <div style="left: 110px;"><math><mpadded height="100px" depth="100px" voffset="1verythickmathspace"><mspace width="10px" height="10px"/></mpadded></math></div>
-      <div style="left: 100px;"><math><mpadded height="100px" depth="100px" voffset="0.3333333333333333em"><mspace width="10px" height="10px"/></mpadded></math></div>
-      <!-- veryverythickmathspace -->
-      <div style="left: 130px;"><math><mpadded height="100px" depth="100px" voffset="1veryverythickmathspace"><mspace width="10px" height="10px"/></mpadded></math></div>
-      <div style="left: 120px;"><math><mpadded height="100px" depth="100px" voffset="0.3888888888888889em"><mspace width="10px" height="10px"/></mpadded></math></div>
-      <!-- negativeveryverythinmathspace -->
-      <div style="left: 10px;"><math><mpadded height="100px" depth="100px" voffset="1negativeveryverythinmathspace"><mspace width="10px" height="10px"/></mpadded></math></div>
-      <div style="left: 0px;"><math><mpadded height="100px" depth="100px" voffset="-0.05555555555555556em"><mspace width="10px" height="10px"/></mpadded></math></div>
-      <!-- negativeverythinmathspace -->
-      <div style="left: 30px;"><math><mpadded height="100px" depth="100px" voffset="1negativeverythinmathspace"><mspace width="10px" height="10px"/></mpadded></math></div>
-      <div style="left: 20px;"><math><mpadded height="100px" depth="100px" voffset="-0.1111111111111111em"><mspace width="10px" height="10px"/></mpadded></math></div>
-      <!-- negativethinmathspace -->
-      <div style="left: 50px;"><math><mpadded height="100px" depth="100px" voffset="1negativethinmathspace"><mspace width="10px" height="10px"/></mpadded></math></div>
-      <div style="left: 40px;"><math><mpadded height="100px" depth="100px" voffset="-0.1666666666666667em"><mspace width="10px" height="10px"/></mpadded></math></div>
-      <!-- negativemediummathspace -->
-      <div style="left: 70px;"><math><mpadded height="100px" depth="100px" voffset="1negativemediummathspace"><mspace width="10px" height="10px"/></mpadded></math></div>
-      <div style="left: 60px;"><math><mpadded height="100px" depth="100px" voffset="-0.2222222222222222em"><mspace width="10px" height="10px"/></mpadded></math></div>
-      <!-- negativethickmathspace -->
-      <div style="left: 90px;"><math><mpadded height="100px" depth="100px" voffset="1negativethickmathspace"><mspace width="10px" height="10px"/></mpadded></math></div>
-      <div style="left: 80px;"><math><mpadded height="100px" depth="100px" voffset="-0.2777777777777778em"><mspace width="10px" height="10px"/></mpadded></math></div>
-      <!-- negativeverythickmathspace -->
-      <div style="left: 110px;"><math><mpadded height="100px" depth="100px" voffset="1negativeverythickmathspace"><mspace width="10px" height="10px"/></mpadded></math></div>
-      <div style="left: 100px;"><math><mpadded height="100px" depth="100px" voffset="-0.3333333333333333em"><mspace width="10px" height="10px"/></mpadded></math></div>
-      <!-- negativeveryverythickmathspace -->
-      <div style="left: 130px;"><math><mpadded height="100px" depth="100px" voffset="1negativeveryverythickmathspace"><mspace width="10px" height="10px"/></mpadded></math></div>
-      <div style="left: 120px;"><math><mpadded height="100px" depth="100px" voffset="-0.3888888888888889em"><mspace width="10px" height="10px"/></mpadded></math></div>
-    </div>
-  </div>
+  <div id="log"></div>
+  <p>
+    <math>
+      <mspace id="unitCm" width="2.54cm"/>
+      <mspace id="unitEm" width="12em"/>
+      <mspace id="unitEx" width="100ex"/>
+      <mspace id="unitIn" width="3in"/>
+      <mspace id="unitMm" width="152.4mm"/>
+      <mspace id="unitPc" width="6pc"/>
+      <mstyle mathsize="200%"><mspace id="unitPercentage" width="3em"/></mstyle>
+      <mspace id="unitPt" width="72pt"/>
+      <mspace id="unitPx" width="123px"/>
+      <mstyle mathsize="5"><mspace id="unitNone" width="3em"/></mstyle>
+    </math>
+  </p>
+  <p>
+    <math>
+      <mspace id="spaceCm" width="&#x20;&#x9;&#xA;&#xD;&#x20;&#x9;&#xA;&#xD;2.54cm&#x20;&#x9;&#xA;&#xD;&#x20;&#x9;&#xA;&#xD;"/>
+      <mspace id="spaceEm" width="&#x20;&#x9;&#xA;&#xD;&#x20;&#x9;&#xA;&#xD;12em&#x20;&#x9;&#xA;&#xD;&#x20;&#x9;&#xA;&#xD;"/>
+      <mspace id="spaceEx" width="&#x20;&#x9;&#xA;&#xD;&#x20;&#x9;&#xA;&#xD;100ex&#x20;&#x9;&#xA;&#xD;&#x20;&#x9;&#xA;&#xD;"/>
+      <mspace id="spaceIn" width="&#x20;&#x9;&#xA;&#xD;&#x20;&#x9;&#xA;&#xD;3in&#x20;&#x9;&#xA;&#xD;&#x20;&#x9;&#xA;&#xD;"/>
+      <mspace id="spaceMm" width="&#x20;&#x9;&#xA;&#xD;&#x20;&#x9;&#xA;&#xD;152.4mm&#x20;&#x9;&#xA;&#xD;&#x20;&#x9;&#xA;&#xD;"/>
+      <mspace id="spacePc" width="&#x20;&#x9;&#xA;&#xD;&#x20;&#x9;&#xA;&#xD;6pc&#x20;&#x9;&#xA;&#xD;&#x20;&#x9;&#xA;&#xD;"/>
+      <mstyle mathsize="200%"><mspace id="spacePercentage" width="&#x20;&#x9;&#xA;&#xD;&#x20;&#x9;&#xA;&#xD;3em&#x20;&#x9;&#xA;&#xD;&#x20;&#x9;&#xA;&#xD;"/></mstyle>
+      <mspace id="spacePt" width="&#x20;&#x9;&#xA;&#xD;&#x20;&#x9;&#xA;&#xD;72pt&#x20;&#x9;&#xA;&#xD;&#x20;&#x9;&#xA;&#xD;"/>
+      <mspace id="spacePx" width="&#x20;&#x9;&#xA;&#xD;&#x20;&#x9;&#xA;&#xD;123px&#x20;&#x9;&#xA;&#xD;&#x20;&#x9;&#xA;&#xD;"/>
+      <mstyle mathsize="5"><mspace id="spaceNone" width="&#x20;&#x9;&#xA;&#xD;&#x20;&#x9;&#xA;&#xD;3em&#x20;&#x9;&#xA;&#xD;&#x20;&#x9;&#xA;&#xD;"/></mstyle>
+    </math>
+  </p>
+  <p>
+    <math>
+      <mspace id="n0" width="0em"/>
+      <mspace id="n1" width="9em"/>
+      <mspace id="n2" width=".8em"/>
+      <mspace id="n3" width="7.em"/>
+      <mspace id="n4" width="65em"/>
+      <mspace id="n5" width="432em"/>
+      <mspace id="n6" width=".10em"/>
+      <mspace id="n7" width=".789em"/>
+      <mspace id="n8" width="6.5em"/>
+      <mspace id="n9" width="43.21em"/>
+      <mspace id="n10" width="012.345em"/>
+    </math>
+  </p>
+  <p>
+    <math>
+      <mspace id="ref"></mspace>
+      <mpadded voffset="-0em"><mspace id="N0"/></mpadded>
+      <mpadded voffset="-9em"><mspace id="N1"/></mpadded>
+      <mpadded voffset="-.8em"><mspace id="N2"/></mpadded>
+      <mpadded voffset="-7.em"><mspace id="N3"/></mpadded>
+      <mpadded voffset="-65em"><mspace id="N4"/></mpadded>
+      <mpadded voffset="-432em"><mspace id="N5"/></mpadded>
+      <mpadded voffset="-.10em"><mspace id="N6"/></mpadded>
+      <mpadded voffset="-.789em"><mspace id="N7"/></mpadded>
+      <mpadded voffset="-6.5em"><mspace id="N8"/></mpadded>
+      <mpadded voffset="-43.21em"><mspace id="N9"/></mpadded>
+      <mpadded voffset="-012.345em"><mspace id="N10"/></mpadded>
+    </math>
+  </p>
+  <p>
+    <math>
+      <mrow id="veryverythinmathspace">
+        <mspace width="1em"/>
+        <mspace width="veryverythinmathspace"/>
+        <mspace/>
+      </mrow>
+      <mrow id="verythinmathspace">
+        <mspace width="1em"/>
+        <mspace width="verythinmathspace"/>
+        <mspace/>
+      </mrow>
+      <mrow id="thinmathspace">
+        <mspace width="1em"/>
+        <mspace width="thinmathspace"/>
+        <mspace/>
+      </mrow>
+      <mrow id="mediummathspace">
+        <mspace width="1em"/>
+        <mspace width="mediummathspace"/>
+        <mspace/>
+      </mrow>
+      <mrow id="thickmathspace">
+        <mspace width="1em"/>
+        <mspace width="thickmathspace"/>
+        <mspace/>
+      </mrow>
+      <mrow id="verythickmathspace">
+        <mspace width="1em"/>
+        <mspace width="verythickmathspace"/>
+        <mspace/>
+      </mrow>
+      <mrow id="veryverythickmathspace">
+        <mspace width="1em"/>
+        <mspace width="veryverythickmathspace"/>
+        <mspace/>
+      </mrow>
+    </math>
+    <math>
+      <mrow id="negativeveryverythinmathspace">
+        <mspace width="1em"/>
+        <mspace width="veryverythinmathspace"/>
+        <mspace/>
+      </mrow>
+      <mrow id="negativeverythinmathspace">
+        <mspace width="1em"/>
+        <mspace width="verythinmathspace"/>
+        <mspace/>
+      </mrow>
+      <mrow id="negativethinmathspace">
+        <mspace width="1em"/>
+        <mspace width="thinmathspace"/>
+        <mspace/>
+      </mrow>
+      <mrow id="negativemediummathspace">
+        <mspace width="1em"/>
+        <mspace width="mediummathspace"/>
+        <mspace/>
+      </mrow>
+      <mrow id="negativethickmathspace">
+        <mspace width="1em"/>
+        <mspace width="thickmathspace"/>
+        <mspace/>
+      </mrow>
+      <mrow id="negativeverythickmathspace">
+        <mspace width="1em"/>
+        <mspace width="verythickmathspace"/>
+        <mspace/>
+      </mrow>
+      <mrow id="negativeveryverythickmathspace">
+        <mspace width="1em"/>
+        <mspace width="veryverythickmathspace"/>
+        <mspace/>
+      </mrow>
+    </math>
+  </p>
 </body>
 </html>
diff --git a/testing/web-platform/tests/mathml/relations/css-styling/lengths-3.html b/testing/web-platform/tests/mathml/relations/css-styling/lengths-3.html
deleted file mode 100644
index aa38e9729d..0000000000
--- a/testing/web-platform/tests/mathml/relations/css-styling/lengths-3.html
+++ /dev/null
@@ -1,159 +0,0 @@
-<!DOCTYPE html>
-<html>
-<head>
-<meta charset="utf-8">
-<title>MathML lengths</title>
-<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#cssstyling"/>
-<meta name="assert" content="Verify various cases of the MathML length syntax.">
-<script src="/resources/testharness.js"></script>
-<script src="/resources/testharnessreport.js"></script>
-<style>
-  @font-face {
-    font-family: TestFont;
-    src: url("/fonts/math/xheight500.woff");
-  }
-  math {
-    font-family: TestFont;
-    font-size: 10px;
-  }
-</style>
-<script>
-  var epsilon = .5;
-
-  function getBox(aId) {
-    return document.getElementById(aId).getBoundingClientRect();
-  }
-
-  setup({ explicit_done: true });
-  window.addEventListener("load", function() {
-    // Delay the check to workaround WebKit's bug https://webkit.org/b/174030.
-    requestAnimationFrame(() => { document.fonts.ready.then(runTests); });
-  });
-
-  function runTests() {
-    test(function() {
-      assert_equals(getBox("unitCm").width, 96, "cm");
-      assert_equals(getBox("unitEm").width, 120, "em");
-      assert_equals(getBox("unitEx").width, 500, "ex");
-      assert_equals(getBox("unitIn").width, 288, "in");
-      assert_equals(getBox("unitNamed").width, 700, "namedspace");
-      assert_equals(getBox("unitMm").width, 576, "mm");
-      assert_equals(getBox("unitPc").width, 96, "pc");
-      assert_equals(getBox("unitPercentage").width, 60, "%");
-      assert_equals(getBox("unitPt").width, 96, "pt");
-      assert_equals(getBox("unitPx").width, 123, "px");
-      assert_equals(getBox("unitNone").width, 150, "Unitless");
-    }, "Units");
-
-    test(function() {
-      assert_equals(getBox("spaceCm").width, 96, "cm");
-      assert_equals(getBox("spaceEm").width, 120, "em");
-      assert_equals(getBox("spaceEx").width, 500, "ex");
-      assert_equals(getBox("spaceIn").width, 288, "in");
-      assert_equals(getBox("spaceNamed").width, 700, "namedspace");
-      assert_equals(getBox("spaceMm").width, 576, "mm");
-      assert_equals(getBox("spacePc").width, 96, "pc");
-      assert_equals(getBox("spacePercentage").width, 60, "%");
-      assert_equals(getBox("spacePt").width, 96, "pt");
-      assert_equals(getBox("spacePx").width, 123, "px");
-      assert_equals(getBox("spaceNone").width, 150, "Unitless");
-    }, "Trimming of space");
-
-    test(function() {
-      assert_approx_equals(getBox("n0").width, 0, epsilon, "n0");
-      assert_approx_equals(getBox("n1").width, 90, epsilon, "n1");
-      assert_approx_equals(getBox("n2").width, 8, epsilon, "n2");
-      assert_approx_equals(getBox("n3").width, 70, epsilon, "n3");
-      assert_approx_equals(getBox("n4").width, 650, epsilon, "n4");
-      assert_approx_equals(getBox("n5").width, 4320, epsilon, "n5");
-      assert_approx_equals(getBox("n6").width, 1, epsilon, "n6");
-      assert_approx_equals(getBox("n7").width, 8, epsilon, "n7");
-      assert_approx_equals(getBox("n8").width, 65, epsilon, "n8");
-      assert_approx_equals(getBox("n9").width, 432, epsilon, "n9");
-      assert_approx_equals(getBox("n10").width, 123, epsilon, "n10");
-    }, "Non-negative numbers");
-
-    test(function() {
-      var topRef = getBox("ref").top;
-      assert_approx_equals(getBox("N0").top - topRef, -0, epsilon, "N0");
-      assert_approx_equals(topRef - getBox("N1").top, -90, epsilon, "N1");
-      assert_approx_equals(topRef - getBox("N2").top, -8, epsilon, "N2");
-      assert_approx_equals(topRef - getBox("N3").top, -70, epsilon, "N3");
-      assert_approx_equals(topRef - getBox("N4").top, -650, epsilon, "N4");
-      assert_approx_equals(topRef - getBox("N5").top, -4320, epsilon, "N5");
-      assert_approx_equals(topRef - getBox("N6").top, -1, epsilon, "N6");
-      assert_approx_equals(topRef - getBox("N7").top, -8, epsilon, "N7");
-      assert_approx_equals(topRef - getBox("N8").top, -65, epsilon, "N8");
-      assert_approx_equals(topRef - getBox("N9").top, -432, epsilon, "N9");
-      assert_approx_equals(topRef - getBox("N10").top, -123, epsilon, "N10");
-    }, "Non-positive numbers");
-
-    done();
-  }
-</script>
-</head>
-<body>
-  <div id="log"></div>
-  <p>
-    <math>
-      <mspace id="unitCm" width="2.54cm"/>
-      <mspace id="unitEm" width="12em"/>
-      <mspace id="unitEx" width="100ex"/>
-      <mspace id="unitIn" width="3in"/>
-      <mspace style="font-size: 1800px" id="unitNamed" width="veryverythickmathspace"/>
-      <mspace id="unitMm" width="152.4mm"/>
-      <mspace id="unitPc" width="6pc"/>
-      <mstyle mathsize="200%"><mspace id="unitPercentage" width="3em"/></mstyle>
-      <mspace id="unitPt" width="72pt"/>
-      <mspace id="unitPx" width="123px"/>
-      <mstyle mathsize="5"><mspace id="unitNone" width="3em"/></mstyle>
-    </math>
-  </p>
-  <p>
-    <math>
-      <mspace id="spaceCm" width="&#x20;&#x9;&#xA;&#xD;&#x20;&#x9;&#xA;&#xD;2.54cm&#x20;&#x9;&#xA;&#xD;&#x20;&#x9;&#xA;&#xD;"/>
-      <mspace id="spaceEm" width="&#x20;&#x9;&#xA;&#xD;&#x20;&#x9;&#xA;&#xD;12em&#x20;&#x9;&#xA;&#xD;&#x20;&#x9;&#xA;&#xD;"/>
-      <mspace id="spaceEx" width="&#x20;&#x9;&#xA;&#xD;&#x20;&#x9;&#xA;&#xD;100ex&#x20;&#x9;&#xA;&#xD;&#x20;&#x9;&#xA;&#xD;"/>
-      <mspace id="spaceIn" width="&#x20;&#x9;&#xA;&#xD;&#x20;&#x9;&#xA;&#xD;3in&#x20;&#x9;&#xA;&#xD;&#x20;&#x9;&#xA;&#xD;"/>
-      <mspace style="font-size: 1800px" id="spaceNamed" width="&#x20;&#x9;&#xA;&#xD;&#x20;&#x9;&#xA;&#xD;veryverythickmathspace&#x20;&#x9;&#xA;&#xD;&#x20;&#x9;&#xA;&#xD;"/>
-      <mspace id="spaceMm" width="&#x20;&#x9;&#xA;&#xD;&#x20;&#x9;&#xA;&#xD;152.4mm&#x20;&#x9;&#xA;&#xD;&#x20;&#x9;&#xA;&#xD;"/>
-      <mspace id="spacePc" width="&#x20;&#x9;&#xA;&#xD;&#x20;&#x9;&#xA;&#xD;6pc&#x20;&#x9;&#xA;&#xD;&#x20;&#x9;&#xA;&#xD;"/>
-      <mstyle mathsize="200%"><mspace id="spacePercentage" width="&#x20;&#x9;&#xA;&#xD;&#x20;&#x9;&#xA;&#xD;3em&#x20;&#x9;&#xA;&#xD;&#x20;&#x9;&#xA;&#xD;"/></mstyle>
-      <mspace id="spacePt" width="&#x20;&#x9;&#xA;&#xD;&#x20;&#x9;&#xA;&#xD;72pt&#x20;&#x9;&#xA;&#xD;&#x20;&#x9;&#xA;&#xD;"/>
-      <mspace id="spacePx" width="&#x20;&#x9;&#xA;&#xD;&#x20;&#x9;&#xA;&#xD;123px&#x20;&#x9;&#xA;&#xD;&#x20;&#x9;&#xA;&#xD;"/>
-      <mstyle mathsize="5"><mspace id="spaceNone" width="&#x20;&#x9;&#xA;&#xD;&#x20;&#x9;&#xA;&#xD;3em&#x20;&#x9;&#xA;&#xD;&#x20;&#x9;&#xA;&#xD;"/></mstyle>
-    </math>
-  </p>
-  <p>
-    <math>
-      <mspace id="n0" width="0em"/>
-      <mspace id="n1" width="9em"/>
-      <mspace id="n2" width=".8em"/>
-      <mspace id="n3" width="7.em"/>
-      <mspace id="n4" width="65em"/>
-      <mspace id="n5" width="432em"/>
-      <mspace id="n6" width=".10em"/>
-      <mspace id="n7" width=".789em"/>
-      <mspace id="n8" width="6.5em"/>
-      <mspace id="n9" width="43.21em"/>
-      <mspace id="n10" width="012.345em"/>
-    </math>
-  </p>
-  <p>
-    <math>
-      <mspace id="ref"></mspace>
-      <mpadded voffset="-0em"><mspace id="N0"/></mpadded>
-      <mpadded voffset="-9em"><mspace id="N1"/></mpadded>
-      <mpadded voffset="-.8em"><mspace id="N2"/></mpadded>
-      <mpadded voffset="-7.em"><mspace id="N3"/></mpadded>
-      <mpadded voffset="-65em"><mspace id="N4"/></mpadded>
-      <mpadded voffset="-432em"><mspace id="N5"/></mpadded>
-      <mpadded voffset="-.10em"><mspace id="N6"/></mpadded>
-      <mpadded voffset="-.789em"><mspace id="N7"/></mpadded>
-      <mpadded voffset="-6.5em"><mspace id="N8"/></mpadded>
-      <mpadded voffset="-43.21em"><mspace id="N9"/></mpadded>
-      <mpadded voffset="-012.345em"><mspace id="N10"/></mpadded>
-    </math>
-  </p>
-</body>
-</html>
diff --git a/testing/web-platform/tests/mathml/relations/css-styling/mathsize-attribute-css-keywords-ref.html b/testing/web-platform/tests/mathml/relations/css-styling/mathsize-attribute-css-keywords-ref.html
new file mode 100644
index 0000000000..d24fbf041a
--- /dev/null
+++ b/testing/web-platform/tests/mathml/relations/css-styling/mathsize-attribute-css-keywords-ref.html
@@ -0,0 +1,22 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <meta charset="utf-8"/>
+    <title>mathsize and css keywords</title>
+  </head>
+  <body>
+    <p>Test passes if you see ten "A" of equal size:</p>
+    <math>
+      <mtext>A</mtext>
+      <mtext>A</mtext>
+      <mtext>A</mtext>
+      <mtext>A</mtext>
+      <mtext>A</mtext>
+      <mtext>A</mtext>
+      <mtext>A</mtext>
+      <mtext>A</mtext>
+      <mtext>A</mtext>
+      <mtext>A</mtext>
+    </math>
+  </body>
+</html>
diff --git a/testing/web-platform/tests/mathml/relations/css-styling/mathsize-attribute-css-keywords.html b/testing/web-platform/tests/mathml/relations/css-styling/mathsize-attribute-css-keywords.html
new file mode 100644
index 0000000000..9b3852d0b3
--- /dev/null
+++ b/testing/web-platform/tests/mathml/relations/css-styling/mathsize-attribute-css-keywords.html
@@ -0,0 +1,26 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <meta charset="utf-8"/>
+    <title>mathsize and css keywords</title>
+    <link rel="help" href="https://mathml-refresh.github.io/mathml-core/#css-styling">
+    <link rel="help" href="https://mathml-refresh.github.io/mathml-core/#legacy-mathml-style-attributes">
+    <meta name="assert" content="Verify that CSS font-size keywords are invalid for the mathsize attribute.">
+    <link rel="match" href="mathsize-attribute-css-keywords-ref.html">
+  </head>
+  <body>
+    <p>Test passes if you see ten "A" of equal size:</p>
+    <math>
+      <mtext>A</mtext>
+      <mtext mathsize="xx-small">A</mtext>
+      <mtext mathsize="x-small">A</mtext>
+      <mtext mathsize="small">A</mtext>
+      <mtext mathsize="medium">A</mtext>
+      <mtext mathsize="large">A</mtext>
+      <mtext mathsize="x-large">A</mtext>
+      <mtext mathsize="xx-large">A</mtext>
+      <mtext mathsize="larger">A</mtext>
+      <mtext mathsize="smaller">A</mtext>
+    </math>
+  </body>
+</html>
diff --git a/testing/web-platform/tests/mathml/relations/css-styling/mathsize-attribute-legacy-values-ref.html b/testing/web-platform/tests/mathml/relations/css-styling/mathsize-attribute-legacy-values-ref.html
new file mode 100644
index 0000000000..687efa49be
--- /dev/null
+++ b/testing/web-platform/tests/mathml/relations/css-styling/mathsize-attribute-legacy-values-ref.html
@@ -0,0 +1,16 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <meta charset="utf-8"/>
+    <title>Legacy mathsize values</title>
+  </head>
+  <body>
+    <p>Test passes if you see four "A" of equal size:</p>
+    <math>
+      <mtext>A</mtext>
+      <mtext>A</mtext>
+      <mtext>A</mtext>
+      <mtext>A</mtext>
+    </math>
+  </body>
+</html>
diff --git a/testing/web-platform/tests/mathml/relations/css-styling/mathsize-attribute-legacy-values.html b/testing/web-platform/tests/mathml/relations/css-styling/mathsize-attribute-legacy-values.html
new file mode 100644
index 0000000000..745b103371
--- /dev/null
+++ b/testing/web-platform/tests/mathml/relations/css-styling/mathsize-attribute-legacy-values.html
@@ -0,0 +1,20 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <meta charset="utf-8"/>
+    <title>Legacy mathsize values</title>
+    <link rel="help" href="https://mathml-refresh.github.io/mathml-core/#css-styling">
+    <link rel="help" href="https://mathml-refresh.github.io/mathml-core/#legacy-mathml-style-attributes">
+    <meta name="assert" content="Verify that legacy values for mathsize have no effect.">
+    <link rel="match" href="mathsize-attribute-legacy-values-ref.html">
+  </head>
+  <body>
+    <p>Test passes if you see four "A" of equal size:</p>
+    <math>
+      <mtext>A</mtext>
+      <mtext mathsize="small">A</mtext>
+      <mtext mathsize="medium">A</mtext>
+      <mtext mathsize="big">A</mtext>
+    </math>
+  </body>
+</html>
diff --git a/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-bold-fraktur.html b/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-bold-fraktur.html
index f414181082..8085ad5083 100644
--- a/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-bold-fraktur.html
+++ b/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-bold-fraktur.html
@@ -3,7 +3,9 @@
 <head>
 <meta charset="utf-8"/>
 <title>mathvariant bold-fraktur</title>
-<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#cssproperties"/>
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#css-styling">
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#the-mathvariant-attribute">
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#new-text-transform-values">
 <link rel="match" href="mathvariant-bold-fraktur-ref.html"/>
 <meta name="assert" content="Verify that a single-char <mtext> with a bold-fraktur mathvariant is equivalent to an <mtext> with the transformed unicode character.">
 <style>
diff --git a/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-bold-italic.html b/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-bold-italic.html
index 7b53e986d4..1e1b0b0deb 100644
--- a/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-bold-italic.html
+++ b/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-bold-italic.html
@@ -3,7 +3,9 @@
 <head>
 <meta charset="utf-8"/>
 <title>mathvariant bold-italic</title>
-<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#cssproperties"/>
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#css-styling">
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#the-mathvariant-attribute">
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#new-text-transform-values">
 <link rel="match" href="mathvariant-bold-italic-ref.html"/>
 <meta name="assert" content="Verify that a single-char <mtext> with a bold-italic mathvariant is equivalent to an <mtext> with the transformed unicode character.">
 <style>
diff --git a/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-bold-sans-serif.html b/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-bold-sans-serif.html
index 544db02f2e..cd6cc7a0c5 100644
--- a/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-bold-sans-serif.html
+++ b/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-bold-sans-serif.html
@@ -3,7 +3,9 @@
 <head>
 <meta charset="utf-8"/>
 <title>mathvariant bold-sans-serif</title>
-<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#cssproperties"/>
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#css-styling">
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#the-mathvariant-attribute">
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#new-text-transform-values">
 <link rel="match" href="mathvariant-bold-sans-serif-ref.html"/>
 <meta name="assert" content="Verify that a single-char <mtext> with a bold-sans-serif mathvariant is equivalent to an <mtext> with the transformed unicode character.">
 <style>
diff --git a/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-bold-script.html b/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-bold-script.html
index dc48fbeaaf..8ff7556dac 100644
--- a/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-bold-script.html
+++ b/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-bold-script.html
@@ -3,7 +3,9 @@
 <head>
 <meta charset="utf-8"/>
 <title>mathvariant bold-script</title>
-<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#cssproperties"/>
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#css-styling">
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#the-mathvariant-attribute">
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#new-text-transform-values">
 <link rel="match" href="mathvariant-bold-script-ref.html"/>
 <meta name="assert" content="Verify that a single-char <mtext> with a bold-script mathvariant is equivalent to an <mtext> with the transformed unicode character.">
 <style>
diff --git a/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-bold.html b/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-bold.html
index a51be7b23f..f11594f827 100644
--- a/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-bold.html
+++ b/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-bold.html
@@ -3,7 +3,9 @@
 <head>
 <meta charset="utf-8"/>
 <title>mathvariant bold</title>
-<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#cssproperties"/>
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#css-styling">
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#the-mathvariant-attribute">
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#new-text-transform-values">
 <link rel="match" href="mathvariant-bold-ref.html"/>
 <meta name="assert" content="Verify that a single-char <mtext> with a bold mathvariant is equivalent to an <mtext> with the transformed unicode character.">
 <style>
diff --git a/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-double-struck.html b/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-double-struck.html
index 3090fdc85c..856672bcec 100644
--- a/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-double-struck.html
+++ b/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-double-struck.html
@@ -3,7 +3,9 @@
 <head>
 <meta charset="utf-8"/>
 <title>mathvariant double-struck</title>
-<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#cssproperties"/>
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#css-styling">
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#the-mathvariant-attribute">
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#new-text-transform-values">
 <link rel="match" href="mathvariant-double-struck-ref.html"/>
 <meta name="assert" content="Verify that a single-char <mtext> with a double-struck mathvariant is equivalent to an <mtext> with the transformed unicode character.">
 <style>
diff --git a/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-fraktur.html b/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-fraktur.html
index 8bd15a558b..8ef57a0e2b 100644
--- a/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-fraktur.html
+++ b/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-fraktur.html
@@ -3,7 +3,9 @@
 <head>
 <meta charset="utf-8"/>
 <title>mathvariant fraktur</title>
-<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#cssproperties"/>
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#css-styling">
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#the-mathvariant-attribute">
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#new-text-transform-values">
 <link rel="match" href="mathvariant-fraktur-ref.html"/>
 <meta name="assert" content="Verify that a single-char <mtext> with a fraktur mathvariant is equivalent to an <mtext> with the transformed unicode character.">
 <style>
diff --git a/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-initial.html b/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-initial.html
index 58751bd126..de4b89f7f5 100644
--- a/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-initial.html
+++ b/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-initial.html
@@ -3,7 +3,9 @@
 <head>
 <meta charset="utf-8"/>
 <title>mathvariant initial</title>
-<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#cssproperties"/>
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#css-styling">
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#the-mathvariant-attribute">
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#new-text-transform-values">
 <link rel="match" href="mathvariant-initial-ref.html"/>
 <meta name="assert" content="Verify that a single-char <mtext> with a initial mathvariant is equivalent to an <mtext> with the transformed unicode character.">
 <style>
diff --git a/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-italic.html b/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-italic.html
index 5bcbd322de..4cf3de0456 100644
--- a/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-italic.html
+++ b/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-italic.html
@@ -3,7 +3,9 @@
 <head>
 <meta charset="utf-8"/>
 <title>mathvariant italic</title>
-<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#cssproperties"/>
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#css-styling">
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#the-mathvariant-attribute">
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#new-text-transform-values">
 <link rel="match" href="mathvariant-italic-ref.html"/>
 <meta name="assert" content="Verify that a single-char <mtext> with a italic mathvariant is equivalent to an <mtext> with the transformed unicode character.">
 <style>
diff --git a/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-looped.html b/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-looped.html
index 0326e86e8f..2a774c7716 100644
--- a/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-looped.html
+++ b/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-looped.html
@@ -3,7 +3,9 @@
 <head>
 <meta charset="utf-8"/>
 <title>mathvariant looped</title>
-<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#cssproperties"/>
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#css-styling">
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#the-mathvariant-attribute">
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#new-text-transform-values">
 <link rel="match" href="mathvariant-looped-ref.html"/>
 <meta name="assert" content="Verify that a single-char <mtext> with a looped mathvariant is equivalent to an <mtext> with the transformed unicode character.">
 <style>
diff --git a/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-monospace.html b/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-monospace.html
index 8d9a5d3df2..1c23630ecf 100644
--- a/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-monospace.html
+++ b/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-monospace.html
@@ -3,7 +3,9 @@
 <head>
 <meta charset="utf-8"/>
 <title>mathvariant monospace</title>
-<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#cssproperties"/>
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#css-styling">
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#the-mathvariant-attribute">
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#new-text-transform-values">
 <link rel="match" href="mathvariant-monospace-ref.html"/>
 <meta name="assert" content="Verify that a single-char <mtext> with a monospace mathvariant is equivalent to an <mtext> with the transformed unicode character.">
 <style>
diff --git a/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-sans-serif-bold-italic.html b/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-sans-serif-bold-italic.html
index 21401bc84a..f67a6ab6db 100644
--- a/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-sans-serif-bold-italic.html
+++ b/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-sans-serif-bold-italic.html
@@ -3,7 +3,9 @@
 <head>
 <meta charset="utf-8"/>
 <title>mathvariant sans-serif-bold-italic</title>
-<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#cssproperties"/>
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#css-styling">
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#the-mathvariant-attribute">
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#new-text-transform-values">
 <link rel="match" href="mathvariant-sans-serif-bold-italic-ref.html"/>
 <meta name="assert" content="Verify that a single-char <mtext> with a sans-serif-bold-italic mathvariant is equivalent to an <mtext> with the transformed unicode character.">
 <style>
diff --git a/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-sans-serif-italic.html b/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-sans-serif-italic.html
index 2573872319..ab43df50c5 100644
--- a/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-sans-serif-italic.html
+++ b/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-sans-serif-italic.html
@@ -3,7 +3,9 @@
 <head>
 <meta charset="utf-8"/>
 <title>mathvariant sans-serif-italic</title>
-<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#cssproperties"/>
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#css-styling">
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#the-mathvariant-attribute">
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#new-text-transform-values">
 <link rel="match" href="mathvariant-sans-serif-italic-ref.html"/>
 <meta name="assert" content="Verify that a single-char <mtext> with a sans-serif-italic mathvariant is equivalent to an <mtext> with the transformed unicode character.">
 <style>
diff --git a/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-sans-serif.html b/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-sans-serif.html
index 513e0351cc..bfee81c0cb 100644
--- a/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-sans-serif.html
+++ b/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-sans-serif.html
@@ -3,7 +3,9 @@
 <head>
 <meta charset="utf-8"/>
 <title>mathvariant sans-serif</title>
-<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#cssproperties"/>
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#css-styling">
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#the-mathvariant-attribute">
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#new-text-transform-values">
 <link rel="match" href="mathvariant-sans-serif-ref.html"/>
 <meta name="assert" content="Verify that a single-char <mtext> with a sans-serif mathvariant is equivalent to an <mtext> with the transformed unicode character.">
 <style>
diff --git a/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-script.html b/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-script.html
index efd3f7e8ff..dd7ab6a06d 100644
--- a/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-script.html
+++ b/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-script.html
@@ -3,7 +3,9 @@
 <head>
 <meta charset="utf-8"/>
 <title>mathvariant script</title>
-<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#cssproperties"/>
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#css-styling">
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#the-mathvariant-attribute">
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#new-text-transform-values">
 <link rel="match" href="mathvariant-script-ref.html"/>
 <meta name="assert" content="Verify that a single-char <mtext> with a script mathvariant is equivalent to an <mtext> with the transformed unicode character.">
 <style>
diff --git a/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-stretched.html b/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-stretched.html
index 20c5a39a83..8530c68804 100644
--- a/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-stretched.html
+++ b/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-stretched.html
@@ -3,7 +3,9 @@
 <head>
 <meta charset="utf-8"/>
 <title>mathvariant stretched</title>
-<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#cssproperties"/>
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#css-styling">
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#the-mathvariant-attribute">
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#new-text-transform-values">
 <link rel="match" href="mathvariant-stretched-ref.html"/>
 <meta name="assert" content="Verify that a single-char <mtext> with a stretched mathvariant is equivalent to an <mtext> with the transformed unicode character.">
 <style>
diff --git a/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-tailed.html b/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-tailed.html
index c88d433ce5..823438ec12 100644
--- a/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-tailed.html
+++ b/testing/web-platform/tests/mathml/relations/css-styling/mathvariant-tailed.html
@@ -3,7 +3,9 @@
 <head>
 <meta charset="utf-8"/>
 <title>mathvariant tailed</title>
-<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#cssproperties"/>
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#css-styling">
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#the-mathvariant-attribute">
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#new-text-transform-values">
 <link rel="match" href="mathvariant-tailed-ref.html"/>
 <meta name="assert" content="Verify that a single-char <mtext> with a tailed mathvariant is equivalent to an <mtext> with the transformed unicode character.">
 <style>
diff --git a/testing/web-platform/tests/mathml/relations/css-styling/padding-border-margin/border-001.html b/testing/web-platform/tests/mathml/relations/css-styling/padding-border-margin/border-001.html
new file mode 100644
index 0000000000..38922118ed
--- /dev/null
+++ b/testing/web-platform/tests/mathml/relations/css-styling/padding-border-margin/border-001.html
@@ -0,0 +1,104 @@
+<!DOCTYPE html>
+<html>
+<head>
+<meta charset="utf-8">
+<title>border</title>
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#layout-algorithms">
+<meta name="assert" content="Verify that border is taken into account.">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="helper.js"></script>
+<script>
+  var epsilon = 1;
+
+  setup({ explicit_done: true });
+  window.addEventListener("load", runTests);
+
+  function runTests() {
+      test(function() {
+          var s = measureSpaceAround("mrow-border")
+          assert_approx_equals(s.left, 20, epsilon, "left border");
+          assert_approx_equals(s.right, 30, epsilon, "right border");
+          assert_approx_equals(s.top, 40, epsilon, "top border");
+          assert_approx_equals(s.bottom, 50, epsilon, "bottom border");
+      }, "Border properties on mrow");
+
+      test(function() {
+          var s = measureSpaceAround("mrow-border-shorthand")
+          assert_approx_equals(s.left, 20, epsilon, "left border");
+          assert_approx_equals(s.right, 20, epsilon, "right border");
+          assert_approx_equals(s.top, 20, epsilon, "top border");
+          assert_approx_equals(s.bottom, 20, epsilon, "bottom border");
+      }, "Border properties on mrow (shorthand)");
+
+      test(function() {
+          var s = measureSpaceAround("mrow-border-logical")
+          assert_approx_equals(s.left, 20, epsilon, "left border");
+          assert_approx_equals(s.right, 30, epsilon, "right border");
+          assert_approx_equals(s.top, 40, epsilon, "top border");
+          assert_approx_equals(s.bottom, 50, epsilon, "bottom border");
+      }, "Border properties on mrow (logical)");
+
+      test(function() {
+          var s = measureSpaceAround("mrow-border-logical-shorthand")
+          assert_approx_equals(s.left, 20, epsilon, "left border");
+          assert_approx_equals(s.right, 20, epsilon, "right border");
+          assert_approx_equals(s.top, 30, epsilon, "top border");
+          assert_approx_equals(s.bottom, 30, epsilon, "bottom border");
+      }, "Border properties on mrow (logical, shorthand)");
+
+    done();
+  }
+</script>
+</head>
+<body>
+  <div id="log"></div>
+  <p>
+    <math>
+      <mrow>
+        <mrow id="mrow-border"
+              style="border-left: 20px;
+                     border-right: 30px;
+                     border-top: 40px;
+                     border-bottom: 50px;">
+          <mspace width="50px" height="50px"></mspace>
+        </mrow>
+      </mrow>
+    </math>
+  </p>
+  <p>
+    <math>
+      <mrow>
+        <mrow id="mrow-border-shorthand"
+              style="border: 20px;">
+          <mspace width="50px" height="50px"></mspace>
+        </mrow>
+      </mrow>
+    </math>
+  </p>
+  <p>
+    <math>
+      <mrow>
+        <mrow id="mrow-border-logical"
+              style="border-inline-start: 20px;
+                     border-inline-end: 30px;
+                     border-block-start: 40px;
+                     border-block-end: 50px;">
+          <mspace width="50px" height="50px"></mspace>
+        </mrow>
+      </mrow>
+    </math>
+  </p>
+  <p>
+    <math>
+      <mrow>
+        <mrow id="mrow-border-logical-shorthand"
+              style="border-inline: 20px;
+                     border-block: 30px;">
+          <mspace width="50px" height="50px"></mspace>
+        </mrow>
+      </mrow>
+    </math>
+  </p>
+</body>
+</html>
diff --git a/testing/web-platform/tests/mathml/relations/css-styling/padding-border-margin/border-002.html b/testing/web-platform/tests/mathml/relations/css-styling/padding-border-margin/border-002.html
new file mode 100644
index 0000000000..4168c3cdb9
--- /dev/null
+++ b/testing/web-platform/tests/mathml/relations/css-styling/padding-border-margin/border-002.html
@@ -0,0 +1,51 @@
+<!DOCTYPE html>
+<html>
+<head>
+<meta charset="utf-8">
+<title>border</title>
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#layout-algorithms">
+<meta name="assert" content="Verify that border is taken into account.">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/mathml/support/mathml-fragments.js"></script>
+<script src="helper.js"></script>
+<script>
+  var epsilon = 1;
+
+  setup({ explicit_done: true });
+  window.addEventListener("load", runTests);
+
+  function runTests() {
+
+    for (tag in MathMLFragments) {
+        if (!FragmentHelper.isValidChildOfMrow(tag))
+            continue;
+
+        var style = "border-left: 30px solid; border-right: 40px solid; border-top: 50px solid; border-bottom: 60px solid;";
+
+        if (FragmentHelper.isEmpty(tag)) {
+            test(function() {
+                var s = compareSizeWithAndWithoutStyle(tag, style);
+                assert_approx_equals(s.width_delta, 30 + 40, epsilon, "left/right border");
+                assert_approx_equals(s.height_delta, 50 + 60, epsilon, "top/bottom border");
+            }, `Border properties on ${tag}`);
+            continue;
+        }
+
+        test(function() {
+            var s = compareSpaceWithAndWithoutStyle(tag, style);
+            assert_approx_equals(s.left_delta, 30, epsilon, "left border");
+            assert_approx_equals(s.right_delta, 40, epsilon, "right border");
+            assert_approx_equals(s.top_delta, 50, epsilon, "top border");
+            assert_approx_equals(s.bottom_delta, 60, epsilon, "bottom border");
+        }, `Border properties on ${tag}`);
+    }
+
+    done();
+  }
+</script>
+</head>
+<body>
+  <div id="log"></div>
+</body>
+</html>
diff --git a/testing/web-platform/tests/mathml/relations/css-styling/padding-border-margin/helper.js b/testing/web-platform/tests/mathml/relations/css-styling/padding-border-margin/helper.js
new file mode 100644
index 0000000000..d3f4b261a7
--- /dev/null
+++ b/testing/web-platform/tests/mathml/relations/css-styling/padding-border-margin/helper.js
@@ -0,0 +1,79 @@
+function spaceBetween(childBox, parentBox) {
+    return {
+        left: childBox.left - parentBox.left,
+        right: parentBox.right - childBox.right,
+        top: childBox.top - parentBox.top,
+        bottom: parentBox.bottom - childBox.bottom
+    };
+}
+
+function measureSpaceAround(id) {
+    var mrow = document.getElementById(id);
+    var mrowBox = mrow.getBoundingClientRect();
+    var parentBox = mrow.parentNode.getBoundingClientRect();
+    var childBox = mrow.firstElementChild.getBoundingClientRect();
+    return spaceBetween(childBox, parentBox);
+}
+
+function compareSpaceWithAndWithoutStyle(tag, style) {
+    if (!FragmentHelper.isValidChildOfMrow(tag) ||
+        FragmentHelper.isEmpty(tag))
+        throw `Invalid argument: ${tag}`;
+
+    document.body.insertAdjacentHTML("beforeend", `<div>\
+<math>${MathMLFragments[tag]}</math>\
+<math>${MathMLFragments[tag]}</math>\
+</div>`);
+    var div = document.body.lastElementChild;
+
+    var styleMath = div.firstElementChild;
+    var styleElement = FragmentHelper.element(styleMath);
+    styleElement.setAttribute("style", style);
+    var styleChild = FragmentHelper.forceNonEmptyElement(styleElement);
+    var styleBox = styleMath.getBoundingClientRect();
+    var styleChildBox = styleChild.getBoundingClientRect();
+    var styleSpace = spaceBetween(styleChildBox, styleBox);
+
+    var noStyleMath = div.lastElementChild;
+    var noStyleElement = FragmentHelper.element(noStyleMath);
+    var noStyleChild = FragmentHelper.forceNonEmptyElement(noStyleElement);
+    var noStyleBox = noStyleMath.getBoundingClientRect();
+    var noStyleChildBox = noStyleChild.getBoundingClientRect();
+    var noStyleSpace = spaceBetween(noStyleChildBox, noStyleBox);
+
+    div.style = "display: none;"; // Hide the div after measurement.
+
+    return {
+        left_delta: styleSpace.left - noStyleSpace.left,
+        right_delta: styleSpace.right - noStyleSpace.right,
+        top_delta: styleSpace.top - noStyleSpace.top,
+        bottom_delta: styleSpace.bottom - noStyleSpace.bottom
+    };
+}
+
+function compareSizeWithAndWithoutStyle(tag, style) {
+    if (!FragmentHelper.isValidChildOfMrow(tag))
+        throw `Invalid argument: ${tag}`;
+
+    document.body.insertAdjacentHTML("beforeend", `<div>\
+<math>${MathMLFragments[tag]}</math>\
+<math>${MathMLFragments[tag]}</math>\
+</div>`);
+    var div = document.body.lastElementChild;
+
+    var styleMath = div.firstElementChild;
+    var styleElement = FragmentHelper.element(styleMath);
+    styleElement.setAttribute("style", style);
+    var styleBox = styleMath.getBoundingClientRect();
+
+    var noStyleMath = div.lastElementChild;
+    var noStyleElement = FragmentHelper.element(noStyleMath);
+    var noStyleBox = noStyleMath.getBoundingClientRect();
+
+    div.style = "display: none;"; // Hide the div after measurement.
+
+    return {
+        width_delta: styleBox.width - noStyleBox.width,
+        height_delta: styleBox.height - noStyleBox.height
+    };
+};
diff --git a/testing/web-platform/tests/mathml/relations/css-styling/padding-border-margin/margin-001.html b/testing/web-platform/tests/mathml/relations/css-styling/padding-border-margin/margin-001.html
new file mode 100644
index 0000000000..dc3a2b4a15
--- /dev/null
+++ b/testing/web-platform/tests/mathml/relations/css-styling/padding-border-margin/margin-001.html
@@ -0,0 +1,104 @@
+<!DOCTYPE html>
+<html>
+<head>
+<meta charset="utf-8">
+<title>margin</title>
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#layout-algorithms">
+<meta name="assert" content="Verify that margin is taken into account.">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="helper.js"></script>
+<script>
+  var epsilon = 1;
+
+  setup({ explicit_done: true });
+  window.addEventListener("load", runTests);
+
+  function runTests() {
+      test(function() {
+          var s = measureSpaceAround("mrow-margin")
+          assert_approx_equals(s.left, 20, epsilon, "left margin");
+          assert_approx_equals(s.right, 30, epsilon, "right margin");
+          assert_approx_equals(s.top, 40, epsilon, "top margin");
+          assert_approx_equals(s.bottom, 50, epsilon, "bottom margin");
+      }, "Margin properties on mrow");
+
+      test(function() {
+          var s = measureSpaceAround("mrow-margin-shorthand")
+          assert_approx_equals(s.left, 20, epsilon, "left margin");
+          assert_approx_equals(s.right, 20, epsilon, "right margin");
+          assert_approx_equals(s.top, 20, epsilon, "top margin");
+          assert_approx_equals(s.bottom, 20, epsilon, "bottom margin");
+      }, "Margin properties on mrow (shorthand)");
+
+      test(function() {
+          var s = measureSpaceAround("mrow-margin-logical")
+          assert_approx_equals(s.left, 20, epsilon, "left margin");
+          assert_approx_equals(s.right, 30, epsilon, "right margin");
+          assert_approx_equals(s.top, 40, epsilon, "top margin");
+          assert_approx_equals(s.bottom, 50, epsilon, "bottom margin");
+      }, "Margin properties on mrow (logical)");
+
+      test(function() {
+          var s = measureSpaceAround("mrow-margin-logical-shorthand")
+          assert_approx_equals(s.left, 20, epsilon, "left margin");
+          assert_approx_equals(s.right, 20, epsilon, "right margin");
+          assert_approx_equals(s.top, 30, epsilon, "top margin");
+          assert_approx_equals(s.bottom, 30, epsilon, "bottom margin");
+      }, "Margin properties on mrow (logical, shorthand)");
+
+    done();
+  }
+</script>
+</head>
+<body>
+  <div id="log"></div>
+  <p>
+    <math>
+      <mrow>
+        <mrow id="mrow-margin"
+              style="margin-left: 20px;
+                     margin-right: 30px;
+                     margin-top: 40px;
+                     margin-bottom: 50px;">
+          <mspace width="50px" height="50px"></mspace>
+        </mrow>
+      </mrow>
+    </math>
+  </p>
+  <p>
+    <math>
+      <mrow>
+        <mrow id="mrow-margin-shorthand"
+              style="margin: 20px;">
+          <mspace width="50px" height="50px"></mspace>
+        </mrow>
+      </mrow>
+    </math>
+  </p>
+  <p>
+    <math>
+      <mrow>
+        <mrow id="mrow-margin-logical"
+              style="margin-inline-start: 20px;
+                     margin-inline-end: 30px;
+                     margin-block-start: 40px;
+                     margin-block-end: 50px;">
+          <mspace width="50px" height="50px"></mspace>
+        </mrow>
+      </mrow>
+    </math>
+  </p>
+  <p>
+    <math>
+      <mrow>
+        <mrow id="mrow-margin-logical-shorthand"
+              style="margin-inline: 20px;
+                     margin-block: 30px;">
+          <mspace width="50px" height="50px"></mspace>
+        </mrow>
+      </mrow>
+    </math>
+  </p>
+</body>
+</html>
diff --git a/testing/web-platform/tests/mathml/relations/css-styling/padding-border-margin/margin-002.html b/testing/web-platform/tests/mathml/relations/css-styling/padding-border-margin/margin-002.html
new file mode 100644
index 0000000000..8631be586e
--- /dev/null
+++ b/testing/web-platform/tests/mathml/relations/css-styling/padding-border-margin/margin-002.html
@@ -0,0 +1,51 @@
+<!DOCTYPE html>
+<html>
+<head>
+<meta charset="utf-8">
+<title>margin</title>
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#layout-algorithms">
+<meta name="assert" content="Verify that margin is taken into account.">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/mathml/support/mathml-fragments.js"></script>
+<script src="helper.js"></script>
+<script>
+  var epsilon = 1;
+
+  setup({ explicit_done: true });
+  window.addEventListener("load", runTests);
+
+  function runTests() {
+
+    for (tag in MathMLFragments) {
+        if (!FragmentHelper.isValidChildOfMrow(tag))
+            continue;
+
+        var style = "margin-left: 30px; margin-right: 40px;  margin-top: 50px; margin-bottom: 60px;";
+
+        if (FragmentHelper.isEmpty(tag)) {
+            test(function() {
+                var s = compareSizeWithAndWithoutStyle(tag, style);
+                assert_approx_equals(s.width_delta, 30 + 40, epsilon, "left/right margin");
+                assert_approx_equals(s.height_delta, 50 + 60, epsilon, "top/bottom margin");
+            }, `Margin properties on ${tag}`);
+            continue;
+        }
+
+        test(function() {
+            var s = compareSpaceWithAndWithoutStyle(tag, style);
+            assert_approx_equals(s.left_delta, 30, epsilon, "left margin");
+            assert_approx_equals(s.right_delta, 40, epsilon, "right margin");
+            assert_approx_equals(s.top_delta, 50, epsilon, "top margin");
+            assert_approx_equals(s.bottom_delta, 60, epsilon, "bottom margin");
+        }, `Margin properties on ${tag}`);
+    }
+
+    done();
+  }
+</script>
+</head>
+<body>
+  <div id="log"></div>
+</body>
+</html>
diff --git a/testing/web-platform/tests/mathml/relations/css-styling/padding-border-margin/padding-001.html b/testing/web-platform/tests/mathml/relations/css-styling/padding-border-margin/padding-001.html
new file mode 100644
index 0000000000..1f8875f657
--- /dev/null
+++ b/testing/web-platform/tests/mathml/relations/css-styling/padding-border-margin/padding-001.html
@@ -0,0 +1,104 @@
+<!DOCTYPE html>
+<html>
+<head>
+<meta charset="utf-8">
+<title>padding</title>
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#layout-algorithms">
+<meta name="assert" content="Verify that padding is taken into account.">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="helper.js"></script>
+<script>
+  var epsilon = 1;
+
+  setup({ explicit_done: true });
+  window.addEventListener("load", runTests);
+
+  function runTests() {
+      test(function() {
+          var s = measureSpaceAround("mrow-padding")
+          assert_approx_equals(s.left, 20, epsilon, "left padding");
+          assert_approx_equals(s.right, 30, epsilon, "right padding");
+          assert_approx_equals(s.top, 40, epsilon, "top padding");
+          assert_approx_equals(s.bottom, 50, epsilon, "bottom padding");
+      }, "Padding properties on mrow");
+
+      test(function() {
+          var s = measureSpaceAround("mrow-padding-shorthand")
+          assert_approx_equals(s.left, 20, epsilon, "left padding");
+          assert_approx_equals(s.right, 20, epsilon, "right padding");
+          assert_approx_equals(s.top, 20, epsilon, "top padding");
+          assert_approx_equals(s.bottom, 20, epsilon, "bottom padding");
+      }, "Padding properties on mrow (shorthand)");
+
+      test(function() {
+          var s = measureSpaceAround("mrow-padding-logical")
+          assert_approx_equals(s.left, 20, epsilon, "left padding");
+          assert_approx_equals(s.right, 30, epsilon, "right padding");
+          assert_approx_equals(s.top, 40, epsilon, "top padding");
+          assert_approx_equals(s.bottom, 50, epsilon, "bottom padding");
+      }, "Padding properties on mrow (logical)");
+
+      test(function() {
+          var s = measureSpaceAround("mrow-padding-logical-shorthand")
+          assert_approx_equals(s.left, 20, epsilon, "left padding");
+          assert_approx_equals(s.right, 20, epsilon, "right padding");
+          assert_approx_equals(s.top, 30, epsilon, "top padding");
+          assert_approx_equals(s.bottom, 30, epsilon, "bottom padding");
+      }, "Padding properties on mrow (logical, shorthand)");
+
+    done();
+  }
+</script>
+</head>
+<body>
+  <div id="log"></div>
+  <p>
+    <math>
+      <mrow>
+        <mrow id="mrow-padding"
+              style="padding-left: 20px;
+                     padding-right: 30px;
+                     padding-top: 40px;
+                     padding-bottom: 50px;">
+          <mspace width="50px" height="50px"></mspace>
+        </mrow>
+      </mrow>
+    </math>
+  </p>
+  <p>
+    <math>
+      <mrow>
+        <mrow id="mrow-padding-shorthand"
+              style="padding: 20px;">
+          <mspace width="50px" height="50px"></mspace>
+        </mrow>
+      </mrow>
+    </math>
+  </p>
+  <p>
+    <math>
+      <mrow>
+        <mrow id="mrow-padding-logical"
+              style="padding-inline-start: 20px;
+                     padding-inline-end: 30px;
+                     padding-block-start: 40px;
+                     padding-block-end: 50px;">
+          <mspace width="50px" height="50px"></mspace>
+        </mrow>
+      </mrow>
+    </math>
+  </p>
+  <p>
+    <math>
+      <mrow>
+        <mrow id="mrow-padding-logical-shorthand"
+              style="padding-inline: 20px;
+                     padding-block: 30px;">
+          <mspace width="50px" height="50px"></mspace>
+        </mrow>
+      </mrow>
+    </math>
+  </p>
+</body>
+</html>
diff --git a/testing/web-platform/tests/mathml/relations/css-styling/padding-border-margin/padding-002.html b/testing/web-platform/tests/mathml/relations/css-styling/padding-border-margin/padding-002.html
new file mode 100644
index 0000000000..eadff36b46
--- /dev/null
+++ b/testing/web-platform/tests/mathml/relations/css-styling/padding-border-margin/padding-002.html
@@ -0,0 +1,51 @@
+<!DOCTYPE html>
+<html>
+<head>
+<meta charset="utf-8">
+<title>padding</title>
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#layout-algorithms">
+<meta name="assert" content="Verify that padding is taken into account.">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/mathml/support/mathml-fragments.js"></script>
+<script src="helper.js"></script>
+<script>
+  var epsilon = 1;
+
+  setup({ explicit_done: true });
+  window.addEventListener("load", runTests);
+
+  function runTests() {
+
+    for (tag in MathMLFragments) {
+        if (!FragmentHelper.isValidChildOfMrow(tag))
+            continue;
+
+        var style = "padding-left: 30px; padding-right: 40px;  padding-top: 50px; padding-bottom: 60px;";
+
+        if (FragmentHelper.isEmpty(tag)) {
+            test(function() {
+                var s = compareSizeWithAndWithoutStyle(tag, style);
+                assert_approx_equals(s.width_delta, 30 + 40, epsilon, "left/right padding");
+                assert_approx_equals(s.height_delta, 50 + 60, epsilon, "top/bottom padding");
+            }, `Padding properties on ${tag}`);
+            continue;
+        }
+
+        test(function() {
+            var s = compareSpaceWithAndWithoutStyle(tag, style);
+            assert_approx_equals(s.left_delta, 30, epsilon, "left padding");
+            assert_approx_equals(s.right_delta, 40, epsilon, "right padding");
+            assert_approx_equals(s.top_delta, 50, epsilon, "top padding");
+            assert_approx_equals(s.bottom_delta, 60, epsilon, "bottom padding");
+        }, `Padding properties on ${tag}`);
+    }
+
+    done();
+  }
+</script>
+</head>
+<body>
+  <div id="log"></div>
+</body>
+</html>
diff --git a/testing/web-platform/tests/mathml/relations/css-styling/padding-border-margin/padding-003.html b/testing/web-platform/tests/mathml/relations/css-styling/padding-border-margin/padding-003.html
new file mode 100644
index 0000000000..cad4a990b1
--- /dev/null
+++ b/testing/web-platform/tests/mathml/relations/css-styling/padding-border-margin/padding-003.html
@@ -0,0 +1,39 @@
+<!DOCTYPE html>
+<html>
+<head>
+<meta charset="utf-8">
+<title>padding</title>
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#layout-algorithms">
+<meta name="assert" content="Verify that padding is taken into account.">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/mathml/support/mathml-fragments.js"></script>
+<script src="helper.js"></script>
+<script>
+  var epsilon = 1;
+
+  setup({ explicit_done: true });
+  window.addEventListener("load", runTests);
+
+  function runTests() {
+
+    for (tag in MathMLFragments) {
+        if (!FragmentHelper.isEmpty(tag))
+            continue;
+
+        test(function() {
+            var style = "padding-left: 10px; padding-right: 20px;  padding-top: 15px; padding-bottom: 25px;";
+            var s = compareSizeWithAndWithoutStyle(tag, style);
+            assert_approx_equals(s.width_delta, 10 + 20, epsilon, "padding left/right");
+            assert_approx_equals(s.height_delta, 15 + 25, epsilon, "padding top/bottom");
+        }, `Padding properties on ${tag}`);
+    }
+
+    done();
+  }
+</script>
+</head>
+<body>
+  <div id="log"></div>
+</body>
+</html>
diff --git a/testing/web-platform/tests/mathml/relations/css-styling/visibility-1.html b/testing/web-platform/tests/mathml/relations/css-styling/visibility-1.html
index c84f97aeeb..7083ef70fb 100644
--- a/testing/web-platform/tests/mathml/relations/css-styling/visibility-1.html
+++ b/testing/web-platform/tests/mathml/relations/css-styling/visibility-1.html
@@ -3,7 +3,11 @@
 <head>
 <meta charset="utf-8">
 <title>visibility</title>
-<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#cssstyling">
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#css-styling">
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#text-mtext">
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#fraction-with-nonzero-line-thickness">
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#radical-symbol">
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#enclose-expression-inside-notation-menclose">
 <link rel="match" href="visibility-1-ref.html"/>
 <meta name="assert" content="Verify that visibility=hidden is used for text and graphical elements.">
 </head>
diff --git a/testing/web-platform/tests/mathml/relations/css-styling/writing-mode/writing-mode-001.html b/testing/web-platform/tests/mathml/relations/css-styling/writing-mode/writing-mode-001.html
new file mode 100644
index 0000000000..01a93eb15f
--- /dev/null
+++ b/testing/web-platform/tests/mathml/relations/css-styling/writing-mode/writing-mode-001.html
@@ -0,0 +1,121 @@
+<!DOCTYPE html>
+<html>
+<head>
+<meta charset="utf-8">
+<title>writing mode</title>
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#layout-algorithms">
+<meta name="assert" content="Verify CSS writing mode (writing-mode and directionproperties) for mrow.">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/mathml/support/feature-detection.js"></script>
+<script src="/mathml/support/layout-comparison.js"></script>
+<script>
+  var epsilon = 1;
+
+  setup({ explicit_done: true });
+  window.addEventListener("load", runTests);
+
+  function runTests() {
+      var reference = document.getElementById("horizontal-tb_ltr");
+
+      ["horizontal-tb_rtl",
+       "vertical-lr_ltr",
+       "vertical-lr_rtl",
+       "vertical-rl_ltr",
+       "vertical-rl_rtl"].forEach(id => {
+           var element = document.getElementById(id);
+
+           test(function() {
+               var style = window.getComputedStyle(element);
+               var writingMode = id.split("_");
+               assert_equals(style.getPropertyValue("writing-mode"),
+                             writingMode[0], "writing-mode");
+               assert_equals(style.getPropertyValue("direction"),
+                             writingMode[1], "direction");
+           }, `Inheritance of CSS writing-mode and direction (id='${id}')`);
+
+           test(function() {
+              assert_true(MathMLFeatureDetection.has_mspace());
+              compareLayout(element, reference, epsilon);
+           }, `Layout of mrow (id='${id}')`);
+      });
+      done();
+  }
+</script>
+</head>
+<body>
+  <div id="log"></div>
+  <p>
+    <math>
+      <mrow id="horizontal-tb_ltr">
+        <mspace style="background: blue"
+                width="20px" height="30px" depth="40px"></mspace>
+        <mspace style="background: black"
+                width="50px" depth="60px"></mspace>
+        <mspace style="background: yellow"
+                width="70px" height="80px"></mspace>
+      </mrow>
+    </math>
+  </p>
+  <p>
+    <math style="direction: rtl;">
+      <mrow id="horizontal-tb_rtl">
+        <mspace style="background: blue"
+                width="20px" height="30px" depth="40px"></mspace>
+        <mspace style="background: black"
+                width="50px" depth="60px"></mspace>
+        <mspace style="background: yellow"
+                width="70px" height="80px"></mspace>
+      </mrow>
+    </math>
+  </p>
+  <p>
+    <math style="writing-mode: vertical-lr;">
+      <mrow id="vertical-lr_ltr">
+        <mspace style="background: blue"
+                width="20px" height="30px" depth="40px"></mspace>
+        <mspace style="background: black"
+                width="50px" depth="60px"></mspace>
+        <mspace style="background: yellow"
+                width="70px" height="80px"></mspace>
+      </mrow>
+    </math>
+  </p>
+  <p>
+    <math style="writing-mode: vertical-lr; direction: rtl;">
+      <mrow id="vertical-lr_rtl">
+        <mspace style="background: blue"
+                width="20px" height="30px" depth="40px"></mspace>
+        <mspace style="background: black"
+                width="50px" depth="60px"></mspace>
+        <mspace style="background: yellow"
+                width="70px" height="80px"></mspace>
+      </mrow>
+    </math>
+  </p>
+  <p>
+    <math style="writing-mode: vertical-rl;">
+      <mrow id="vertical-rl_ltr">
+        <mspace style="background: blue"
+                width="20px" height="30px" depth="40px"></mspace>
+        <mspace style="background: black"
+                width="50px" depth="60px"></mspace>
+        <mspace style="background: yellow"
+                width="70px" height="80px"></mspace>
+      </mrow>
+    </math>
+  </p>
+  <p>
+    <math style="writing-mode: vertical-rl; direction: rtl;">
+      <mrow id="vertical-rl_rtl">
+        <mspace style="background: blue"
+                width="20px" height="30px" depth="40px"></mspace>
+        <mspace style="background: black"
+                width="50px" depth="60px"></mspace>
+        <mspace style="background: yellow"
+                width="70px" height="80px"></mspace>
+      </mrow>
+    </math>
+  </p>
+</body>
+</html>
diff --git a/testing/web-platform/tests/mathml/relations/html5-tree/class-1.html b/testing/web-platform/tests/mathml/relations/html5-tree/class-1.html
index ee4b4b50d3..a1efbd2184 100644
--- a/testing/web-platform/tests/mathml/relations/html5-tree/class-1.html
+++ b/testing/web-platform/tests/mathml/relations/html5-tree/class-1.html
@@ -3,7 +3,8 @@
 <head>
 <meta charset="utf-8"/>
 <title>Class</title>
-<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#mathmltree"/>
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#attributes-common-to-html-and-mathml-elements">
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#css-styling">
 <link rel="match" href="class-1-ref.html"/>
 <meta name="assert" content="Verify that the class attribute affects CSS selectors.">
 <style>
diff --git a/testing/web-platform/tests/mathml/relations/html5-tree/class-2.html b/testing/web-platform/tests/mathml/relations/html5-tree/class-2.html
index 4e1ae6b707..8d6515af9f 100644
--- a/testing/web-platform/tests/mathml/relations/html5-tree/class-2.html
+++ b/testing/web-platform/tests/mathml/relations/html5-tree/class-2.html
@@ -3,7 +3,8 @@
 <head>
 <meta charset="utf-8">
 <title>Class</title>
-<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#mathmltree">
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#attributes-common-to-html-and-mathml-elements">
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#dom-and-javascript">
 <meta name="assert" content="Verify whether the getElementsByClassName() works for MathML elements.">
 <script src="/resources/testharness.js"></script>
 <script src="/resources/testharnessreport.js"></script>
diff --git a/testing/web-platform/tests/mathml/relations/html5-tree/color-attributes-1.html b/testing/web-platform/tests/mathml/relations/html5-tree/color-attributes-1.html
index 6f9f93721a..585aebaf39 100644
--- a/testing/web-platform/tests/mathml/relations/html5-tree/color-attributes-1.html
+++ b/testing/web-platform/tests/mathml/relations/html5-tree/color-attributes-1.html
@@ -3,7 +3,8 @@
 <head>
 <meta charset="utf-8"/>
 <title>Color Attributes</title>
-<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#mathmltree"/>
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#css-styling">
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#legacy-mathml-style-attributes">
 <meta name="assert" content="Verify that the mathcolor and mathbackground attributes are supported on the math element.">
 <link rel="match" href="color-attributes-1-ref.html"/>
 <style>
diff --git a/testing/web-platform/tests/mathml/relations/html5-tree/display-1.html b/testing/web-platform/tests/mathml/relations/html5-tree/display-1.html
index 77038ee223..3a180f5d42 100644
--- a/testing/web-platform/tests/mathml/relations/html5-tree/display-1.html
+++ b/testing/web-platform/tests/mathml/relations/html5-tree/display-1.html
@@ -3,7 +3,8 @@
 <head>
 <meta charset="utf-8"/>
 <title>MathML display attribute</title>
-<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#mathmltree">
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#css-styling">
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#the-top-level-math-element">
 <meta name="assert" content="Verify that the display attribute on the math element is supported and impacts centering and line breaking with surrounding content.">
 <script src="/resources/testharness.js"></script>
 <script src="/resources/testharnessreport.js"></script>
diff --git a/testing/web-platform/tests/mathml/relations/html5-tree/dynamic-1.html b/testing/web-platform/tests/mathml/relations/html5-tree/dynamic-1.html
index 48fdd25915..b4d603a9aa 100644
--- a/testing/web-platform/tests/mathml/relations/html5-tree/dynamic-1.html
+++ b/testing/web-platform/tests/mathml/relations/html5-tree/dynamic-1.html
@@ -3,7 +3,7 @@
 <head>
 <meta charset="utf-8"/>
 <title>Dynamic MathML DOM</title>
-<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#dom"/>
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#dom-and-javascript"/>
 <link rel="match" href="dynamic-1-ref.html"/>
 <meta name="assert" content="Verify that the MathML DOM tree can be modified via javascript and that the rendering is correctly updated.">
 <style>
diff --git a/testing/web-platform/tests/mathml/relations/html5-tree/href-click-1.html b/testing/web-platform/tests/mathml/relations/html5-tree/href-click-1.html
index dd6b7990a3..bf902b5e8f 100644
--- a/testing/web-platform/tests/mathml/relations/html5-tree/href-click-1.html
+++ b/testing/web-platform/tests/mathml/relations/html5-tree/href-click-1.html
@@ -3,7 +3,8 @@
 <head>
 <meta charset="utf-8"/>
 <title>href click</title>
-<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#mathmltree">
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#attributes-common-to-html-and-mathml-elements">
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#dom-and-javascript">
 <link rel="match" href="href-click-1-ref.html"/>
 <meta name="assert" content="Verify that a click on a link moves to the target.">
 <script type="text/javascript">
diff --git a/testing/web-platform/tests/mathml/relations/html5-tree/href-click-2.html b/testing/web-platform/tests/mathml/relations/html5-tree/href-click-2.html
index 4c5253df15..c23d87c235 100644
--- a/testing/web-platform/tests/mathml/relations/html5-tree/href-click-2.html
+++ b/testing/web-platform/tests/mathml/relations/html5-tree/href-click-2.html
@@ -3,7 +3,8 @@
 <head>
 <meta charset="utf-8"/>
 <title>href click</title>
-<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#mathmltree">
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#attributes-common-to-html-and-mathml-elements">
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#dom-and-javascript">
 <link rel="match" href="href-click-2-ref.html"/>
 <meta name="assert" content="Verify that a click on an element bubbles to an ancestor link.">
 <script type="text/javascript">
diff --git a/testing/web-platform/tests/mathml/relations/html5-tree/href-click-3.html b/testing/web-platform/tests/mathml/relations/html5-tree/href-click-3.html
index f2863febc1..a8475ea3ff 100644
--- a/testing/web-platform/tests/mathml/relations/html5-tree/href-click-3.html
+++ b/testing/web-platform/tests/mathml/relations/html5-tree/href-click-3.html
@@ -3,7 +3,8 @@
 <head>
 <meta charset="utf-8">
 <title>href click</title>
-<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#mathmltree">
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#attributes-common-to-html-and-mathml-elements">
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#dom-and-javascript">
 <script src="/resources/testharness.js"></script>
 <script src="/resources/testharnessreport.js"></script>
 <script src="/resources/testdriver.js"></script>
diff --git a/testing/web-platform/tests/mathml/relations/html5-tree/integration-point-1.html b/testing/web-platform/tests/mathml/relations/html5-tree/integration-point-1.html
index 3221a67503..4d10af86c7 100644
--- a/testing/web-platform/tests/mathml/relations/html5-tree/integration-point-1.html
+++ b/testing/web-platform/tests/mathml/relations/html5-tree/integration-point-1.html
@@ -3,7 +3,7 @@
 <head>
 <meta charset="utf-8"/>
 <title>MathML inside foreignObject</title>
-<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#dom"/>
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#html-and-svg">
 <link rel="match" href="integration-point-1-ref.html"/>
 <meta name="assert" content="Verify that MathML can be used inside a foreignObject element.">
 </head>
diff --git a/testing/web-platform/tests/mathml/relations/html5-tree/integration-point-2.html b/testing/web-platform/tests/mathml/relations/html5-tree/integration-point-2.html
index d42eeb03ed..20d499d3f8 100644
--- a/testing/web-platform/tests/mathml/relations/html5-tree/integration-point-2.html
+++ b/testing/web-platform/tests/mathml/relations/html5-tree/integration-point-2.html
@@ -3,7 +3,7 @@
 <head>
 <meta charset="utf-8"/>
 <title>MathML as a phrasing content</title>
-<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#dom"/>
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#html-and-svg">
 <link rel="match" href="integration-point-2-ref.html"/>
 <meta name="assert" content="Verify that MathML can be used at positions where phrasing content is accepted.">
 <style type="text/css">
diff --git a/testing/web-platform/tests/mathml/relations/html5-tree/integration-point-3.html b/testing/web-platform/tests/mathml/relations/html5-tree/integration-point-3.html
index 1feb8317ff..1f62d8e630 100644
--- a/testing/web-platform/tests/mathml/relations/html5-tree/integration-point-3.html
+++ b/testing/web-platform/tests/mathml/relations/html5-tree/integration-point-3.html
@@ -3,7 +3,7 @@
 <head>
 <meta charset="utf-8"/>
 <title>phrasing content inside mtext</title>
-<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#dom"/>
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#html-and-svg">
 <link rel="match" href="integration-point-3-ref.html"/>
 <meta name="assert" content="Verify that <mtext> can contain phrasing content">
 <style type="text/css">
diff --git a/testing/web-platform/tests/mathml/relations/html5-tree/required-extensions-2.html b/testing/web-platform/tests/mathml/relations/html5-tree/required-extensions-2.html
index 1d7af04d9e..e1d7a85370 100644
--- a/testing/web-platform/tests/mathml/relations/html5-tree/required-extensions-2.html
+++ b/testing/web-platform/tests/mathml/relations/html5-tree/required-extensions-2.html
@@ -3,7 +3,7 @@
 <head>
 <meta charset="utf-8"/>
 <title>SVG requiredExtensions</title>
-<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#dom"/>
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#html-and-svg">
 <link rel="match" href="required-extensions-2-ref.html"/>
 <meta name="assert" content="Verify that a foreignObject with MathML used as a requiredExtensions value is selected for display in a SVG switch element.">
 </head>
diff --git a/testing/web-platform/tests/mathml/relations/html5-tree/unique-identifier-1.html b/testing/web-platform/tests/mathml/relations/html5-tree/unique-identifier-1.html
index 42a547ac21..e2315f1499 100644
--- a/testing/web-platform/tests/mathml/relations/html5-tree/unique-identifier-1.html
+++ b/testing/web-platform/tests/mathml/relations/html5-tree/unique-identifier-1.html
@@ -3,7 +3,7 @@
 <head>
 <meta charset="utf-8"/>
 <title>Unique identifier</title>
-<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#mathmltree"/>
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#attributes-common-to-html-and-mathml-elements">
 <link rel="match" href="unique-identifier-1-ref.html"/>
 <meta name="assert" content="Verify that the id on a MathML element can be used as a fragment identifier in order to force initial scrolling.">
 </head>
diff --git a/testing/web-platform/tests/mathml/relations/html5-tree/unique-identifier-2.html b/testing/web-platform/tests/mathml/relations/html5-tree/unique-identifier-2.html
index 421ad7a86d..2c3190c51e 100644
--- a/testing/web-platform/tests/mathml/relations/html5-tree/unique-identifier-2.html
+++ b/testing/web-platform/tests/mathml/relations/html5-tree/unique-identifier-2.html
@@ -3,7 +3,8 @@
 <head>
 <meta charset="utf-8">
 <title>Unique Identifier</title>
-<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#mathmltree">
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#attributes-common-to-html-and-mathml-elements">
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#dom-and-javascript">
 <meta name="assert" content="Verify whether the getElementById() works for MathML elements.">
 <script src="/resources/testharness.js"></script>
 <script src="/resources/testharnessreport.js"></script>
diff --git a/testing/web-platform/tests/mathml/relations/html5-tree/unique-identifier-3.html b/testing/web-platform/tests/mathml/relations/html5-tree/unique-identifier-3.html
index c58e5026cf..7cfac89e85 100644
--- a/testing/web-platform/tests/mathml/relations/html5-tree/unique-identifier-3.html
+++ b/testing/web-platform/tests/mathml/relations/html5-tree/unique-identifier-3.html
@@ -3,7 +3,8 @@
 <head>
 <meta charset="utf-8"/>
 <title>Unique Identifier</title>
-<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#mathmltree"/>
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#attributes-common-to-html-and-mathml-elements">
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#css-styling">
 <link rel="match" href="unique-identifier-3-ref.html"/>
 <meta name="assert" content="Verify that the id attribute affects CSS selectors.">
 <style>
diff --git a/testing/web-platform/tests/mathml/relations/text-and-math/use-typo-metrics-1.html b/testing/web-platform/tests/mathml/relations/text-and-math/use-typo-metrics-1.html
index 3797aef5fc..4e92a84646 100644
--- a/testing/web-platform/tests/mathml/relations/text-and-math/use-typo-metrics-1.html
+++ b/testing/web-platform/tests/mathml/relations/text-and-math/use-typo-metrics-1.html
@@ -1,7 +1,7 @@
 <!DOCTYPE html>
 <meta charset="utf-8"/>
 <title>Open Font Format: USE_TYPO_METRICS</title>
-<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#openfontformat"/>
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#text-layout"/>
 <link rel="match" href="use-typo-metrics-1-ref.html"/>
 <meta name="assert" content="Verify that the USE_TYPO_METRICS flag from the OS/2 table is taken into account to calculate line height.">
 <style>
diff --git a/testing/web-platform/tests/mathml/support/layout-comparison.js b/testing/web-platform/tests/mathml/support/layout-comparison.js
new file mode 100644
index 0000000000..ee62502e1a
--- /dev/null
+++ b/testing/web-platform/tests/mathml/support/layout-comparison.js
@@ -0,0 +1,86 @@
+function getWritingMode(element, reference) {
+    var style = window.getComputedStyle(reference);
+    if (style.getPropertyValue("writing-mode") !== "horizontal-tb" ||
+        style.getPropertyValue("direction") !== "ltr")
+        throw "Reference should have writing mode horizontal-tb and ltr";
+
+    style = window.getComputedStyle(element);
+    var param =  {
+        rtl: style.getPropertyValue("direction") === "rtl",
+        mode: style.getPropertyValue("writing-mode")
+    };
+
+    return param;
+}
+
+function compareSize(element, reference, epsilon) {
+    var param = getWritingMode(element, reference);
+    var elementBox = element.getBoundingClientRect();
+    var referenceBox = reference.getBoundingClientRect();
+
+    switch(param.mode) {
+    case "horizontal-tb":
+        assert_approx_equals(elementBox.width, referenceBox.width, epsilon,
+                             "inline size");
+        assert_approx_equals(elementBox.height, referenceBox.height, epsilon,
+                             "block size");
+        break;
+    case "vertical-lr":
+    case "vertical-rl":
+        assert_approx_equals(elementBox.width, referenceBox.height, epsilon,
+                             "inline size");
+        assert_approx_equals(elementBox.height, referenceBox.width, epsilon,
+                             "block size");
+        break;
+    default:
+        throw "compareSize: Unrecognized writing-mode value";
+    }
+}
+
+function compareLayout(element, reference, epsilon) {
+    if (element.children.length != reference.children.length)
+        throw "Reference should have the same number of children."
+
+    // Compare sizes of elements and children.
+    var param = getWritingMode(element, reference);
+
+    compareSize(element, reference, epsilon);
+    var elementBox = element.getBoundingClientRect();
+    var referenceBox = reference.getBoundingClientRect();
+    for (var i = 0; i < element.children.length; i++) {
+        compareSize(element.children[i], reference.children[i], epsilon);
+
+        var childBox = element.children[i].getBoundingClientRect();
+        var referenceChildBox = reference.children[i].getBoundingClientRect();
+
+        switch(param.mode) {
+        case "horizontal-tb":
+            if (!param.rtl)
+                throw "compareLayout: unexpected writing-mode value";
+            assert_approx_equals(elementBox.right - childBox.right,
+                                 referenceChildBox.left - referenceBox.left,
+                                 epsilon,
+                                 `inline position (child ${i})`);
+            assert_approx_equals(childBox.top - elementBox.top,
+                                 referenceChildBox.top - referenceBox.top,
+                                 epsilon,
+                                 `block position (child ${i})`);
+            break;
+        case "vertical-lr":
+        case "vertical-rl":
+            assert_approx_equals(param.rtl ?
+                                 elementBox.bottom - childBox.bottom :
+                                 childBox.top - elementBox.top,
+                                 referenceChildBox.left - referenceBox.left,
+                                 epsilon,
+                                 `inline position (child ${i})`);
+            assert_approx_equals(elementBox.right - childBox.right,
+                                 referenceChildBox.top - referenceBox.top,
+                                 epsilon,
+                                 `block position (child ${i})`);
+            break;
+        default:
+            throw "compareLayout: Unrecognized writing-mode value";
+        }
+    }
+}
diff --git a/testing/web-platform/tests/mathml/support/mathml-fragments.js b/testing/web-platform/tests/mathml/support/mathml-fragments.js
new file mode 100644
index 0000000000..3753c3460e
--- /dev/null
+++ b/testing/web-platform/tests/mathml/support/mathml-fragments.js
@@ -0,0 +1,151 @@
+var MathMLFragments = {
+    "annotation": "\
+<semantics>\
+  <mrow></mrow>\
+  <annotation class='element text-container'></annotation>\
+</semantics>",
+    "annotation-xml": "\
+<semantics>\
+  <mrow></mrow>\
+  <annotation-xml class='element text-container foreign-container'></annotation-xml>\
+</semantics>",
+    "maction": "\
+<maction class='element' actiontype='statusline'>\
+  <mrow class='mathml-container'></mrow>\
+  <mtext class='text-container'></mtext>\
+</maction>",
+    "menclose": "<menclose class='element mathml-container'></menclose>",
+    "merror": "<merror class='element mathml-container'></merror>",
+    "mfrac": "\
+<mfrac class='element'>\
+  <mrow class='mathml-container'></mrow>\
+  <mrow class='mathml-container'></mrow>\
+</mfrac>",
+    "mi": "<mi class='element text-container foreign-container'></mi>",
+    "mmultiscripts": "\
+<mmultiscripts class='element'>\
+  <mrow class='mathml-container'></mrow>\
+  <mrow class='mathml-container'></mrow>\
+  <mrow class='mathml-container'></mrow>\
+</mmultiscripts>",
+    "mn": "<mn class='element text-container foreign-container'></mn>",
+    "mo": "<mo class='element text-container foreign-container'></mo>",
+    "mover": "\
+<mover class='element'>\
+  <mrow class='mathml-container'></mrow>\
+  <mrow class='mathml-container'></mrow>\
+</mover>",
+    "mpadded": "<mpadded class='element mathml-container'></mpadded>",
+    "mphantom": "<mphantom class='element mathml-container'></mphantom>",
+    "mprescripts": "\
+<mmultiscripts>\
+  <mrow class='mathml-container'></mrow>\
+  <mprescripts class='element'/>\
+  <mrow class='mathml-container'></mrow>\
+  <mrow class='mathml-container'></mrow>\
+</mmultiscripts>",
+    "mroot": "\
+<mroot class='element'>\
+  <mrow class='mathml-container'></mrow>\
+  <mrow class='mathml-container'></mrow>\
+</mroot>",
+    "mrow": "<mrow class='element mathml-container'></mrow>",
+    "ms": "<ms class='element text-container foreign-container'></ms>",
+    "mspace": "<mspace class='element'></mspace>",
+    "msqrt": "<msqrt class='element mathml-container'></msqrt>",
+    "mstyle": "<mstyle class='element mathml-container'></mstyle>",
+    "msub": "\
+<msub class='element mathml-container'>\
+  <mrow class='mathml-container'></mrow>\
+  <mrow class='mathml-container'></mrow>\
+</msub>",
+    "msubsup": "\
+<msubsup class='element mathml-container'>\
+  <mrow class='mathml-container'></mrow>\
+  <mrow class='mathml-container'></mrow>\
+  <mrow class='mathml-container'></mrow>\
+</msubsup>",
+    "msup": "\
+<msup class='element mathml-container'>\
+  <mrow class='mathml-container'></mrow>\
+  <mrow class='mathml-container'></mrow>\
+</msup>",
+    "mtable": "\
+<mtable class='element'>\
+  <mtr>\
+    <mtd class='mathml-container'>\
+    </mtd>\
+  </mtr>\
+</mtable>",
+    "mtd": "\
+<mtable>\
+  <mtr>\
+    <mtd class='element mathml-container'>\
+    </mtd>\
+  </mtr>\
+</mtable>",
+    "mtext": "<mtext class='element text-container foreign-container'></mtext>",
+    "mtr": "\
+<mtable>\
+  <mtr class='element'>\
+    <mtd class='mathml-container'>\
+    </mtd>\
+  </mtr>\
+</mtable>",
+    "munder": "\
+<munder class='element'>\
+  <mrow class='mathml-container'></mrow>\
+  <mrow class='mathml-container'></mrow>\
+</munder>",
+    "munderover": "\
+<munderover class='element'>\
+  <mrow class='mathml-container'></mrow>\
+  <mrow class='mathml-container'></mrow>\
+  <mrow class='mathml-container'></mrow>\
+</munderover>",
+    "none": "\
+<mmultiscripts>\
+  <mrow class='mathml-container'></mrow>\
+  <none class='element'/>\
+  <mrow class='mathml-container'></mrow>\
+</mmultiscripts>",
+    "semantics": "\
+<semantics class='element'>\
+  <mrow class='mathml-container'></mrow>\
+  <annotation class='text-container'></annotation>\
+</semantics>"
+};
+
+var FragmentHelper = {
+    createElement: function(tag) {
+        return document.createElementNS("http://www.w3.org/1998/Math/MathML", tag);
+    },
+
+    isValidChildOfMrow: function(tag) {
+        return !(tag == "annotation" ||
+                 tag == "annotation-xml" ||
+                 tag == "mprescripts" ||
+                 tag == "none" ||
+                 tag == "mtr" ||
+                 tag == "mtd");
+    },
+
+    isEmpty: function(tag) {
+        return tag === "mspace" || tag == "mprescripts" || tag == "none";
+    },
+
+    element: function(fragment) {
+        return fragment.getElementsByClassName('element')[0];
+    },
+
+    forceNonEmptyElement: function(fragment) {
+        var element = this.element(fragment) || fragment;
+        if (element.firstElementChild)
+            return element.firstElementChild;
+        if (element.classList.contains("mathml-container"))
+            return element.appendChild(this.createElement("mrow"));
+        if (element.classList.contains("foreign-container"))
+            return element.appendChild(document.createElement("span"));
+        throw "Cannot make the element nonempty";
+    }
+}
diff --git a/testing/web-platform/tests/mathml/tools/mathvariant-transforms.py b/testing/web-platform/tests/mathml/tools/mathvariant-transforms.py
index ba99b595f0..51c7c187a1 100644
--- a/testing/web-platform/tests/mathml/tools/mathvariant-transforms.py
+++ b/testing/web-platform/tests/mathml/tools/mathvariant-transforms.py
@@ -81,7 +81,9 @@ for mathvariant in mathvariantTransforms:
     reftest.write(source % mathvariant)
     reftestReference.write(source % ("%s (reference)" % mathvariant))
     source ='\
-<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#cssproperties"/>\n\
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#css-styling">\n\
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#the-mathvariant-attribute">\n\
+<link rel="help" href="https://mathml-refresh.github.io/mathml-core/#new-text-transform-values">\n\
 <link rel="match" href="mathvariant-%s-ref.html"/>\n\
 <meta name="assert" content="Verify that a single-char <mtext> with a %s mathvariant is equivalent to an <mtext> with the transformed unicode character.">\n'
     reftest.write(source % (mathvariant, mathvariant))
diff --git a/testing/web-platform/tests/navigation-timing/buffered-flag.window.js b/testing/web-platform/tests/navigation-timing/buffered-flag.window.js
new file mode 100644
index 0000000000..c6b1e0bc85
--- /dev/null
+++ b/testing/web-platform/tests/navigation-timing/buffered-flag.window.js
@@ -0,0 +1,16 @@
+async_test(t => {
+  function checkEntryList(entries) {
+    assert_equals(entries.length, 1, "Only one navigation timing entry");
+    assert_equals(entries[0].entryType, "navigation", "entryType is \"navigation\"");
+    assert_equals(entries[0].name, window.location.toString(), "name is the address of the document");
+  }
+  // First observer creates second in callback to ensure the entry has been dispatched by the time
+  // the second observer begins observing.
+  new PerformanceObserver(t.step_func(entryList => {
+    checkEntryList(entryList.getEntries());
+    // Second observer requires 'buffered: true' to see the navigation entry.
+    new PerformanceObserver(t.step_func_done(list => {
+      checkEntryList(list.getEntries());
+    })).observe({type: 'navigation', buffered: true});
+  })).observe({entryTypes: ["navigation"]});
+}, "PerformanceObserver with buffered flag sees previous navigation entry.");
diff --git a/testing/web-platform/tests/navigation-timing/test_document_onload.html b/testing/web-platform/tests/navigation-timing/test_document_onload.html
new file mode 100644
index 0000000000..fd38555449
--- /dev/null
+++ b/testing/web-platform/tests/navigation-timing/test_document_onload.html
@@ -0,0 +1,48 @@
+<!DOCTYPE html>
+<html>
+    <head>
+        <meta charset="utf-8">
+        <title>window.performance.navigation attributes</title>
+        <link rel="author" title="Mozilla" href="https://www.mozilla.org/" />
+        <link rel="help" href="https://www.w3.org/TR/navigation-timing-2/#processing-model"/>
+        <script src="/resources/testharness.js"></script>
+        <script src="/resources/testharnessreport.js"></script>
+        <script src="/common/performance-timeline-utils.js"></script>
+        <script src="resources/webperftestharness.js"></script>
+    </head>
+    <body>
+        <h1>Description</h1>
+        <p>This test checks that the transferSize, encodedBodySize and decodedBodySize attributes have correct values when checked in the onload handler</p>
+
+        <div id="log"></div>
+
+        <script>
+            async_test(async function (t) {
+                document.addEventListener("DOMContentLoaded", t.step_func_done(() => {
+                    let entry = window.performance.getEntriesByType("navigation")[0];
+                    assert_greater_than(entry.transferSize, 1000, "descr");
+                    assert_greater_than(entry.encodedBodySize, 1000, "descr");
+                    assert_greater_than(entry.decodedBodySize, 1000, "descr");
+                }));
+            }, "Test that the attributes have a proper value during DOMContentLoaded");
+
+            async_test(async function (t) {
+                window.addEventListener("load", t.step_func_done(() => {
+                    let entry = window.performance.getEntriesByType("navigation")[0];
+                    assert_greater_than(entry.transferSize, 1000, "descr");
+                    assert_greater_than(entry.encodedBodySize, 1000, "descr");
+                    assert_greater_than(entry.decodedBodySize, 1000, "descr");
+                    async_test(async function (t) {
+                        setTimeout(t.step_func_done(() => {
+                          let entry = window.performance.getEntriesByType("navigation")[0];
+                          assert_greater_than(entry.transferSize, 1000, "descr");
+                          assert_greater_than(entry.encodedBodySize, 1000, "descr");
+                          assert_greater_than(entry.decodedBodySize, 1000, "descr");
+                        }), 0);
+                    }, "Test that the attributes have a proper value during a task after onload");
+                }));
+            }, "Test that the attributes have a proper value during onload");
+
+        </script>
+    </body>
+</html>
diff --git a/testing/web-platform/tests/paint-timing/basetest.html b/testing/web-platform/tests/paint-timing/basetest.html
index 7f84566d9a..1c87598459 100644
--- a/testing/web-platform/tests/paint-timing/basetest.html
+++ b/testing/web-platform/tests/paint-timing/basetest.html
@@ -9,6 +9,7 @@
 
 <script>
 async_test(function(t) {
+    assert_implements(window.PerformancePaintTiming, "Paint Timing isn't supported.");
     t.step(function() {
         const bufferedEntries = performance.getEntriesByType('paint');
         assert_equals(bufferedEntries.length, 0, "No paint entries yet");
diff --git a/testing/web-platform/tests/paint-timing/buffered-flag.window.js b/testing/web-platform/tests/paint-timing/buffered-flag.window.js
new file mode 100644
index 0000000000..b3a6a6374c
--- /dev/null
+++ b/testing/web-platform/tests/paint-timing/buffered-flag.window.js
@@ -0,0 +1,35 @@
+async_test(t => {
+  assert_implements(window.PerformancePaintTiming, "Paint Timing isn't supported.");
+  // First observer creates second in callback to ensure the entry has been dispatched by the time
+  // the second observer begins observing.
+  let entries_seen = 0;
+  new PerformanceObserver(firstList => {
+    entries_seen += firstList.getEntries().length;
+    // Abort if we have not yet received both paint entries.
+    if (entries_seen < 2)
+      return;
+
+    // Second observer requires 'buffered: true' to see the entries.
+    let firstPaintSeen = false;
+    let firstContentfulPaintSeen = false;
+    new PerformanceObserver(list => {
+      list.getEntries().forEach(t.step_func(entry => {
+        assert_equals(entry.entryType, 'paint');
+        if (entry.name === 'first-paint')
+          firstPaintSeen = true;
+        else if (entry.name === 'first-contentful-paint')
+          firstContentfulPaintSeen = true;
+        else
+          assert_unreached('The observer should only see first paint or first contentful paint!');
+
+        if (firstPaintSeen && firstContentfulPaintSeen)
+          t.done();
+      }));
+    }).observe({'type': 'paint', buffered: true});
+  }).observe({'entryTypes': ['paint']});
+
+  // Trigger the first paint entries
+  const img = document.createElement("IMG");
+  img.src = "resources/circles.png";
+  document.body.appendChild(img);
+}, "PerformanceObserver with buffered flag sees previous paint entries.");
diff --git a/testing/web-platform/tests/paint-timing/child-painting-first-image.html b/testing/web-platform/tests/paint-timing/child-painting-first-image.html
index 4671604cf0..a7ed2c6f10 100644
--- a/testing/web-platform/tests/paint-timing/child-painting-first-image.html
+++ b/testing/web-platform/tests/paint-timing/child-painting-first-image.html
@@ -5,6 +5,7 @@
 
 <script>
 async_test(function (t) {
+    assert_implements(window.PerformancePaintTiming, "Paint Timing isn't supported.");
     window.addEventListener('message', t.step_func(e => {
         assert_equals(e.data, '2 paint first-paint paint first-contentful-paint');
         // When only child frame paints, expect only first-paint.
diff --git a/testing/web-platform/tests/paint-timing/fcp-only/fcp-canvas-context.html b/testing/web-platform/tests/paint-timing/fcp-only/fcp-canvas-context.html
index 18eb07bfde..077c1aa3dd 100644
--- a/testing/web-platform/tests/paint-timing/fcp-only/fcp-canvas-context.html
+++ b/testing/web-platform/tests/paint-timing/fcp-only/fcp-canvas-context.html
@@ -9,13 +9,13 @@
 <canvas id="canvas" width="50" height="50"></canvas>
 <script>
   promise_test(async t => {
-    assert_precondition(window.PerformancePaintTiming, "Paint Timing isn't supported.");
+    assert_implements(window.PerformancePaintTiming, "Paint Timing isn't supported.");
     await new Promise(r => window.addEventListener('load', r));
-    await assertNoFirstContentfulPaint();
+    await assertNoFirstContentfulPaint(t);
     const canvas = document.getElementById('canvas');
     const context = canvas.getContext('2d');
     context.fillRect(0, 0, 100, 100);
-    await assertFirstContentfulPaint();
+    await assertFirstContentfulPaint(t);
   }, 'Canvas should count as contentful when context is created');
 </script>
 </body>
diff --git a/testing/web-platform/tests/paint-timing/fcp-only/fcp-ensure-update-the-rendering-step.html b/testing/web-platform/tests/paint-timing/fcp-only/fcp-ensure-update-the-rendering-step.html
new file mode 100644
index 0000000000..700707de33
--- /dev/null
+++ b/testing/web-platform/tests/paint-timing/fcp-only/fcp-ensure-update-the-rendering-step.html
@@ -0,0 +1,55 @@
+<!DOCTYPE html>
+<head>
+    <title>
+      Ensure the timing is marked during the `update the rendering` step.
+    </title>
+</head>
+<style>
+    #main {
+        width: 100px;
+        height: 100px;
+        left: 0px;
+        position: relative;
+        top: 0;
+        background-image: url(../resources/circles.png);
+        opacity: 0;
+    }
+
+    #main.contentful {
+        opacity: 0.1;
+    }
+</style>
+<body>
+<script src="../resources/utils.js"></script>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<div id="main"></div>
+<script>
+setup({"hide_test_state": true});
+async_test(function (t) {
+    assert_implements(window.PerformancePaintTiming, "Paint Timing isn't supported.");
+    let fired = false;
+    const main = document.getElementById('main');
+    let animationFrameStamps = [];
+    requestAnimationFrame(function frame(stamp) {
+        animationFrameStamps.unshift(stamp);
+        main.className = "contentful";
+        while (performance.now() - stamp <= 5) {
+          /* Busy-wait */
+        }
+        if(!fired)
+            requestAnimationFrame(frame);
+    });
+    new PerformanceObserver(t.step_func(list=>{
+        for (let entry of list.getEntries()) {
+            if (entry.name == "first-contentful-paint") {
+                fired = true;
+                assert_any(assert_approx_equals, entry.startTime, animationFrameStamps, 1, "One of the past requestAnimationFrame should have the same timestamp as paint entry");
+                t.done();
+            }
+        }
+    })).observe({type: "paint"});
+}, 'The first-contentful-paint timestamp should be same as the last RAF');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/paint-timing/fcp-only/fcp-gradient.html b/testing/web-platform/tests/paint-timing/fcp-only/fcp-gradient.html
index 3a356f3dd1..b9f86d8dd7 100644
--- a/testing/web-platform/tests/paint-timing/fcp-only/fcp-gradient.html
+++ b/testing/web-platform/tests/paint-timing/fcp-only/fcp-gradient.html
@@ -16,10 +16,9 @@
 <div id="main"></div>
 <script>
   promise_test(async t => {
-      assert_precondition(window.PerformancePaintTiming, "Paint Timing isn't supported.");
-      const main = document.getElementById('main');
+      assert_implements(window.PerformancePaintTiming, "Paint Timing isn't supported.");
       await new Promise(r => window.addEventListener('load', r));
-      await assertNoFirstContentfulPaint();
+      await assertNoFirstContentfulPaint(t);
   },  'Gradients should not count as contentful');
 </script>
 </body>
diff --git a/testing/web-platform/tests/paint-timing/fcp-only/fcp-text-input.html b/testing/web-platform/tests/paint-timing/fcp-only/fcp-text-input.html
new file mode 100644
index 0000000000..0b7e568359
--- /dev/null
+++ b/testing/web-platform/tests/paint-timing/fcp-only/fcp-text-input.html
@@ -0,0 +1,23 @@
+<!DOCTYPE html>
+<head>
+<title>Performance Paint Timing Test: FCP due for non-empty text input</title>
+</head>
+<body>
+<script src="../resources/utils.js"></script>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<input id="input" type="text" />
+<script>
+  promise_test(async t => {
+      assert_implements(window.PerformancePaintTiming, "Paint Timing isn't supported.");
+      await new Promise(r => window.addEventListener('load', r));
+      await assertNoFirstContentfulPaint(t);
+      const input = document.getElementById('input');
+      input.setAttribute('value', '  ');
+      await assertNoFirstContentfulPaint(t);
+      input.setAttribute('value', 'value');
+      await assertFirstContentfulPaint(t);
+  }, 'Text input should become contentful when its value is non-empty');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/paint-timing/fcp-only/fcp-typographic-pseudo.html b/testing/web-platform/tests/paint-timing/fcp-only/fcp-typographic-pseudo.html
new file mode 100644
index 0000000000..5ec62b7d59
--- /dev/null
+++ b/testing/web-platform/tests/paint-timing/fcp-only/fcp-typographic-pseudo.html
@@ -0,0 +1,32 @@
+<!DOCTYPE html>
+<head>
+<title>Performance Paint Timing Test: FCP should not fire when all text is hidden due to typographic pseudo-elements</title>
+<style>
+    #main {
+        position: relative;
+        width: 100px;
+        height: 100px;
+    }
+
+    #main *::first-letter {
+        opacity: 0;
+    }
+
+    /* contentful class is defined in test_fcp script. */
+    #main.contentful *::first-letter {
+        opacity: 1;
+    }
+</style>
+</head>
+<body>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="../resources/utils.js"></script>
+<div id="main">
+    <div>A</div>
+</div>
+<script>
+    test_fcp("First contentful paint fires only when some of the text is visible, considering ::first-letter.")
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/paint-timing/fcp-only/fcp-video-frame.html b/testing/web-platform/tests/paint-timing/fcp-only/fcp-video-frame.html
index fff38cd2c8..cdfd167071 100644
--- a/testing/web-platform/tests/paint-timing/fcp-only/fcp-video-frame.html
+++ b/testing/web-platform/tests/paint-timing/fcp-only/fcp-video-frame.html
@@ -9,15 +9,16 @@
 <video id="video" autoplay></video>
 <script>
   promise_test(async t => {
-      assert_precondition(window.PerformancePaintTiming, "Paint Timing isn't supported.");
+      assert_implements(window.PerformancePaintTiming, "Paint Timing isn't supported.");
       await new Promise(r => window.addEventListener('load', r));
-      await assertNoFirstContentfulPaint();
+      await assertNoFirstContentfulPaint(t);
+      // Set actual video content to trigger FCP.
       const video = document.getElementById('video');
       video.setAttribute('src', '/media/test.mp4');
       await new Promise(resolve => {
         video.oncanplay = resolve;
       });
-      await assertFirstContentfulPaint();
+      await assertFirstContentfulPaint(t);
   }, 'Video should become contentful when first frame is loaded');
 </script>
 </body>
diff --git a/testing/web-platform/tests/paint-timing/fcp-only/fcp-video-poster.html b/testing/web-platform/tests/paint-timing/fcp-only/fcp-video-poster.html
index ed9cabcaee..eb9b1399b5 100644
--- a/testing/web-platform/tests/paint-timing/fcp-only/fcp-video-poster.html
+++ b/testing/web-platform/tests/paint-timing/fcp-only/fcp-video-poster.html
@@ -9,9 +9,9 @@
 <video id="video" width="50" height="50"></video>
 <script>
   promise_test(async t => {
-    assert_precondition(window.PerformancePaintTiming, "Paint Timing isn't supported.");
+    assert_implements(window.PerformancePaintTiming, "Paint Timing isn't supported.");
     await new Promise(r => window.addEventListener('load', r));
-    await assertNoFirstContentfulPaint();
+    await assertNoFirstContentfulPaint(t);
     const video = document.getElementById('video');
     const src = '../resources/circles.png';
     const image = new Image();
@@ -20,7 +20,7 @@
     await new Promise(resolve => {
         image.onload = async () => resolve();
     })
-    await assertFirstContentfulPaint();
+    await assertFirstContentfulPaint(t);
   }, 'Video should become contentful when poster is loaded');
 </script>
 </body>
diff --git a/testing/web-platform/tests/paint-timing/fcp-only/fcp-with-rtl.html b/testing/web-platform/tests/paint-timing/fcp-only/fcp-with-rtl.html
new file mode 100644
index 0000000000..e9fc285783
--- /dev/null
+++ b/testing/web-platform/tests/paint-timing/fcp-only/fcp-with-rtl.html
@@ -0,0 +1,30 @@
+<!DOCTYPE html>
+<head>
+<title>Performance Paint Timing Test: FCP due to direction change</title>
+<style>
+  #text {
+    right: -100px;
+    position: absolute;
+  }
+
+  body {
+    direction: rtl;
+  }
+</style>
+</head>
+<body>
+<script src="../resources/utils.js"></script>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<div id="text">TEXT</div>
+<script>
+  promise_test(async t => {
+      assert_implements(window.PerformancePaintTiming, "Paint Timing isn't supported.");
+      await new Promise(r => window.addEventListener('load', r));
+      await assertNoFirstContentfulPaint(t);
+      document.body.style.direction = 'ltr'
+      await assertFirstContentfulPaint(t);
+  }, 'FCP should fire when coordinates are negative, if within document scrollable area');
+</script>
+</body>
+</html>
diff --git a/testing/web-platform/tests/paint-timing/first-contentful-bg-image.html b/testing/web-platform/tests/paint-timing/first-contentful-bg-image.html
index ddcc78fbe5..3da3d2553e 100644
--- a/testing/web-platform/tests/paint-timing/first-contentful-bg-image.html
+++ b/testing/web-platform/tests/paint-timing/first-contentful-bg-image.html
@@ -11,6 +11,7 @@
 <footer>
 <script>
 async_test(function (t) {
+    assert_implements(window.PerformancePaintTiming, "Paint Timing isn't supported.");
     const body = document.getElementsByTagName('body')[0];
     body.style.backgroundImage = 'url(resources/circles.png)';
     window.onload = function() {
diff --git a/testing/web-platform/tests/paint-timing/first-contentful-canvas.html b/testing/web-platform/tests/paint-timing/first-contentful-canvas.html
index 3610a57ec7..667591cfe3 100644
--- a/testing/web-platform/tests/paint-timing/first-contentful-canvas.html
+++ b/testing/web-platform/tests/paint-timing/first-contentful-canvas.html
@@ -9,6 +9,7 @@
 
 <script>
 async_test(function (t) {
+    assert_implements(window.PerformancePaintTiming, "Paint Timing isn't supported.");
     const canvas = document.getElementById("canvas");
     const context = canvas.getContext("2d");
     context.beginPath();
diff --git a/testing/web-platform/tests/paint-timing/first-contentful-image.html b/testing/web-platform/tests/paint-timing/first-contentful-image.html
index a4e89b3765..5c29bfe070 100644
--- a/testing/web-platform/tests/paint-timing/first-contentful-image.html
+++ b/testing/web-platform/tests/paint-timing/first-contentful-image.html
@@ -9,6 +9,7 @@
 
 <script>
 async_test(function (t) {
+    assert_implements(window.PerformancePaintTiming, "Paint Timing isn't supported.");
     const img = document.createElement("IMG");
     img.src = "resources/circles.png";
     img.onload = function() {
diff --git a/testing/web-platform/tests/paint-timing/first-contentful-paint.html b/testing/web-platform/tests/paint-timing/first-contentful-paint.html
index d8eabefe12..de2ac03523 100644
--- a/testing/web-platform/tests/paint-timing/first-contentful-paint.html
+++ b/testing/web-platform/tests/paint-timing/first-contentful-paint.html
@@ -10,6 +10,7 @@
 
 <script>
 async_test(function (t) {
+    assert_implements(window.PerformancePaintTiming, "Paint Timing isn't supported.");
     const bufferedEntries = performance.getEntriesByType('paint');
     assert_equals(bufferedEntries.length, 0, "No paint entries yet");
     const div = document.createElement("div");
diff --git a/testing/web-platform/tests/paint-timing/first-contentful-svg.html b/testing/web-platform/tests/paint-timing/first-contentful-svg.html
index cf3e954275..9909ec659e 100644
--- a/testing/web-platform/tests/paint-timing/first-contentful-svg.html
+++ b/testing/web-platform/tests/paint-timing/first-contentful-svg.html
@@ -9,6 +9,7 @@
 
 <script>
 async_test(function (t) {
+    assert_implements(window.PerformancePaintTiming, "Paint Timing isn't supported.");
     const img = document.createElement("IMG");
     img.src = "resources/circle.svg";
     img.onload = function() {
diff --git a/testing/web-platform/tests/paint-timing/first-image-child.html b/testing/web-platform/tests/paint-timing/first-image-child.html
index 0622ddef96..9b48ff8905 100644
--- a/testing/web-platform/tests/paint-timing/first-image-child.html
+++ b/testing/web-platform/tests/paint-timing/first-image-child.html
@@ -1,26 +1,24 @@
 <!DOCTYPE html>
 <head>
 <title>Performance Paint Timing Test: child ignores parent FCP</title>
+<meta name="timeout" content="long">
 </head>
 <body>
 <script src="/resources/testharness.js"></script>
 <script src="/resources/testharnessreport.js"></script>
-<div id="image"></div>
-
+<iframe src='resources/subframe-sending-paint.html' id='child-iframe'></iframe>
+<img src='resources/circles.png'/>
 <script>
 async_test(function (t) {
-    const iframe = document.createElement('iframe');
-    iframe.id = 'child-iframe';
-    iframe.src = 'resources/subframe-sending-paint.html';
-    document.body.appendChild(iframe);
+    assert_implements(window.PerformancePaintTiming, "Paint Timing isn't supported.");
+
     window.addEventListener('message', t.step_func(e => {
         // Child iframe should not have any paint-timing entries.
         assert_equals(e.data, '0');
         t.done();
     }));
-    const img = document.createElement('IMG');
-    img.src = 'resources/circles.png';
-    img.onload = function() {
+    // Wait for onload to ensure img and iframe have loaded.
+    window.addEventListener('load', function() {
         function testPaintEntries() {
             const bufferedEntries = performance.getEntriesByType('paint');
             if (bufferedEntries.length < 2) {
@@ -39,8 +37,7 @@ async_test(function (t) {
             })
         }
         testPaintEntries();
-    };
-    document.getElementById('image').appendChild(img);
+    });
 }, 'Child iframe ignores paint-timing events fired from parent image rendering.');
 </script>
 </body>
diff --git a/testing/web-platform/tests/paint-timing/first-paint-bg-color.html b/testing/web-platform/tests/paint-timing/first-paint-bg-color.html
index 46efb9e267..21271da4ce 100644
--- a/testing/web-platform/tests/paint-timing/first-paint-bg-color.html
+++ b/testing/web-platform/tests/paint-timing/first-paint-bg-color.html
@@ -11,6 +11,7 @@
 <footer>
 <script>
 async_test(function (t) {
+    assert_implements(window.PerformancePaintTiming, "Paint Timing isn't supported.");
     document.body.style.backgroundColor = "#AA0000";
 
     function testPaintEntries() {
diff --git a/testing/web-platform/tests/paint-timing/first-paint-only.html b/testing/web-platform/tests/paint-timing/first-paint-only.html
index fb0e752875..99f41f97b1 100644
--- a/testing/web-platform/tests/paint-timing/first-paint-only.html
+++ b/testing/web-platform/tests/paint-timing/first-paint-only.html
@@ -9,6 +9,7 @@
 
 <script>
 async_test(function (t) {
+    assert_implements(window.PerformancePaintTiming, "Paint Timing isn't supported.");
     const div = document.createElement("div");
     div.style.width = "100px";
     div.style.height = "100px";
diff --git a/testing/web-platform/tests/paint-timing/paint-visited.html b/testing/web-platform/tests/paint-timing/paint-visited.html
index a0734f97ac..d611197b28 100644
--- a/testing/web-platform/tests/paint-timing/paint-visited.html
+++ b/testing/web-platform/tests/paint-timing/paint-visited.html
@@ -9,7 +9,10 @@
 <script src="/resources/testharnessreport.js"></script>
 <a id="link" href="./">link</a>
 <script>
-/* This test ensures that an empty page is painted when there is an invisible visited link (that would be visible if the link was not visited). It's necessary that whether the page is painted or not does not depend on visitedness of the link. Otherwise the paint-timing API could be used to sniff whether a link has been visited or not. */
+/* This test ensures that an empty page is painted when there is an invisible visited link (that
+would be visible if the link was not visited). It's necessary that whether the page is painted or
+not does not depend on visitedness of the link. Otherwise the paint-timing API could be used to
+sniff whether a link has been visited or not. */
 window.onload = function() {
   /* Convenience helper to get the link into the browsing history.
     Using a relative path because some browsers only allow replaceState within the same domain. */
@@ -18,6 +21,7 @@ window.onload = function() {
   history.replaceState({}, "", current_url);
 }
 async_test(function(t) {
+  assert_implements(window.PerformancePaintTiming, "Paint Timing isn't supported.");
   function testPaintEntries() {
       const bufferedEntries = performance.getEntriesByType('paint');
       if (bufferedEntries.length < 2) {
diff --git a/testing/web-platform/tests/paint-timing/resources/utils.js b/testing/web-platform/tests/paint-timing/resources/utils.js
index fb60500f3b..2ee0e3d062 100644
--- a/testing/web-platform/tests/paint-timing/resources/utils.js
+++ b/testing/web-platform/tests/paint-timing/resources/utils.js
@@ -1,15 +1,3 @@
-// Number milliseconds to wait for CSS resources to load.
-const numMillisecondsWait = 50;
-
-// We use requestAnimationFrame() calls to force the user agent to paint and give enough
-// time for FCP to show up in the performance timeline. Hence, set |numFramesWaiting| to
-// 3 and use that constant whenever the test needs to wait for the next paint to occur.
-const numFramesWaiting = 3;
-
-function waitTime(t) {
-  return new Promise(resolve => t.step_timeout(resolve, numMillisecondsWait));
-}
-
 function waitForAnimationFrames(count) {
   return new Promise(resolve => {
     if (count-- <= 0) {
@@ -22,35 +10,39 @@ function waitForAnimationFrames(count) {
   });
 }
 
-// Asserts that there is currently no FCP reported, even after some wait.
+// Asserts that there is currently no FCP reported. Pass t to add some wait, in case CSS is loaded
+// and FCP is incorrectly fired afterwards.
 async function assertNoFirstContentfulPaint(t) {
-  if (t)
-    await waitTime(t);
-
-  await waitForAnimationFrames(numFramesWaiting);
+  await waitForAnimationFrames(3);
   assert_equals(performance.getEntriesByName('first-contentful-paint').length, 0, 'First contentful paint marked too early. ');
 }
 
-// Asserts that FCP is reported, possibly after some wait. The wait is needed
-// because sometimes the FCP relies on some CSS resources to finish loading.
+// Function that is resolved once FCP is reported, using PerformanceObserver. It rejects after a long
+// wait time so that failing tests don't timeout.
 async function assertFirstContentfulPaint(t) {
-  if (t)
-    await waitTime(t);
-  await waitForAnimationFrames(numFramesWaiting);
-  assert_equals(performance.getEntriesByName('first-contentful-paint').length, 1, 'Expected first contentful paint not found. ');
+  return new Promise(resolve  => {
+    function checkFCP() {
+      if (performance.getEntriesByName('first-contentful-paint').length === 1) {
+        resolve();
+      } else {
+        t.step_timeout(checkFCP, 0);
+      }
+    }
+    t.step(checkFCP);
+  });
 }
 
 async function test_fcp(label) {
   const style = document.createElement('style');
   document.head.appendChild(style);
   await promise_test(async t => {
-    assert_precondition(window.PerformancePaintTiming, "Paint Timing isn't supported.");
+    assert_implements(window.PerformancePaintTiming, "Paint Timing isn't supported.");
     const main = document.getElementById('main');
     await new Promise(r => window.addEventListener('load', r));
-    await assertNoFirstContentfulPaint();
+    await assertNoFirstContentfulPaint(t);
     main.className = 'preFCP';
-    await assertNoFirstContentfulPaint();
+    await assertNoFirstContentfulPaint(t);
     main.className = 'contentful';
-    await assertFirstContentfulPaint();
+    await assertFirstContentfulPaint(t);
   }, label);
 }
diff --git a/testing/web-platform/tests/paint-timing/sibling-painting-first-image.html b/testing/web-platform/tests/paint-timing/sibling-painting-first-image.html
index d4197e8a35..d8fec53047 100644
--- a/testing/web-platform/tests/paint-timing/sibling-painting-first-image.html
+++ b/testing/web-platform/tests/paint-timing/sibling-painting-first-image.html
@@ -6,6 +6,7 @@
 <iframe id="listening-iframe" src="resources/subframe-sending-paint.html"></iframe>
 <script>
 async_test(function (t) {
+    assert_implements(window.PerformancePaintTiming, "Paint Timing isn't supported.");
     let paintingIframeHasDispatchedEntries = false;
     window.addEventListener('message', t.step_func(e => {
         if (!paintingIframeHasDispatchedEntries) {
diff --git a/testing/web-platform/tests/paint-timing/supported-paint-type.window.js b/testing/web-platform/tests/paint-timing/supported-paint-type.window.js
index 36acf82ca3..518faff5cf 100644
--- a/testing/web-platform/tests/paint-timing/supported-paint-type.window.js
+++ b/testing/web-platform/tests/paint-timing/supported-paint-type.window.js
@@ -1,25 +1,22 @@
 test(() => {
-  if (typeof PerformanceObserver.supportedEntryTypes === "undefined")
-    assert_unreached("supportedEntryTypes is not supported.");
+  assert_implements(typeof PerformanceObserver.supportedEntryTypes !== "undefined", 'supportedEntryTypes is not supported');
   assert_true(PerformanceObserver.supportedEntryTypes.includes("paint"),
     "There should be an entry 'paint' in PerformanceObserver.supportedEntryTypes");
 }, "supportedEntryTypes contains 'paint'.");
 
-if (typeof PerformanceObserver.supportedEntryTypes !== "undefined") {
-  const entryType = 'paint';
-  if (PerformanceObserver.supportedEntryTypes.includes(entryType)) {
-    promise_test(async() => {
-      await new Promise((resolve) => {
-        new PerformanceObserver(function (list, observer) {
-          observer.disconnect();
-          resolve();
-        }).observe({entryTypes: [entryType]});
+const entryType = 'paint';
+promise_test(async() => {
+  assert_implements(typeof PerformanceObserver.supportedEntryTypes !== "undefined", 'supportedEntryTypes is not supported');
+  assert_implements(typeof PerformanceObserver.supportedEntryTypes.includes(entryType), `supportedEntryTypes does not include '${entryType}'`);
+  await new Promise((resolve) => {
+    new PerformanceObserver(function (list, observer) {
+      observer.disconnect();
+      resolve();
+    }).observe({entryTypes: [entryType]});
 
-        // Force the PerformanceEntry.
-        // Use `self` for Workers.
-        if (self.document)
-          document.head.parentNode.appendChild(document.createTextNode('foo'));
-      })
-    }, `'${entryType}' entries should be observable.`)
-  }
-}
+    // Force the PerformanceEntry.
+    // Use `self` for Workers.
+    if (self.document)
+      document.head.parentNode.appendChild(document.createTextNode('foo'));
+  })
+}, `'${entryType}' entries should be observable.`)
diff --git a/testing/web-platform/tests/performance-timeline/buffered-flag-after-timeout.any.js b/testing/web-platform/tests/performance-timeline/buffered-flag-after-timeout.any.js
new file mode 100644
index 0000000000..08b3e32314
--- /dev/null
+++ b/testing/web-platform/tests/performance-timeline/buffered-flag-after-timeout.any.js
@@ -0,0 +1,11 @@
+async_test(t => {
+  performance.mark('foo');
+  t.step_timeout(() => {
+    // After a timeout, PerformanceObserver should still receive entry if using the buffered flag.
+    new PerformanceObserver(t.step_func_done(list => {
+      const entries = list.getEntries();
+      assert_equals(entries.length, 1, 'There should be 1 mark entry.');
+      assert_equals(entries[0].entryType, 'mark');
+    })).observe({type: 'mark', buffered: true});
+  }, 100);
+}, 'PerformanceObserver with buffered flag sees entry after timeout');
diff --git a/testing/web-platform/tests/performance-timeline/buffered-flag-observer.any.js b/testing/web-platform/tests/performance-timeline/buffered-flag-observer.any.js
new file mode 100644
index 0000000000..31dc39c128
--- /dev/null
+++ b/testing/web-platform/tests/performance-timeline/buffered-flag-observer.any.js
@@ -0,0 +1,15 @@
+async_test( t=> {
+  for (let i = 0; i < 50; i++)
+    performance.mark('foo' + i);
+  let marksCreated = 50;
+  let marksReceived = 0;
+  new PerformanceObserver(list => {
+    marksReceived += list.getEntries().length;
+    if (marksCreated < 100) {
+      performance.mark('bar' + marksCreated);
+      marksCreated++;
+    }
+    if (marksReceived == 100)
+      t.done();
+  }).observe({type: 'mark', buffered: true});
+}, 'PerformanceObserver with buffered flag should see past and future entries.');
diff --git a/testing/web-platform/tests/performance-timeline/multiple-buffered-flag-observers.any.js b/testing/web-platform/tests/performance-timeline/multiple-buffered-flag-observers.any.js
new file mode 100644
index 0000000000..5dd44fb18f
--- /dev/null
+++ b/testing/web-platform/tests/performance-timeline/multiple-buffered-flag-observers.any.js
@@ -0,0 +1,32 @@
+promise_test(() => {
+  // The first promise waits for one buffered flag observer to receive 3 entries.
+  const promise1 = new Promise(resolve1 => {
+    let numObserved1 = 0;
+    new PerformanceObserver((entryList, obs) => {
+      // This buffered flag observer is constructed after a regular observer detects a mark.
+      new PerformanceObserver(list => {
+        numObserved1 += list.getEntries().length;
+        if (numObserved1 == 3)
+          resolve1();
+      }).observe({type: 'mark', buffered: true});
+      obs.disconnect();
+    }).observe({entryTypes: ['mark']});
+    performance.mark('foo');
+  });
+  // The second promise waits for another buffered flag observer to receive 3 entries.
+  const promise2 = new Promise(resolve2 => {
+    step_timeout(() => {
+      let numObserved2 = 0;
+      // This buffered flag observer is constructed after a delay of 100ms.
+      new PerformanceObserver(list => {
+        numObserved2 += list.getEntries().length;
+        if (numObserved2 == 3)
+          resolve2();
+      }).observe({type: 'mark', buffered: true});
+    }, 100);
+    performance.mark('bar');
+  });
+  performance.mark('meow');
+  // Pass if and only if both buffered observers received all 3 mark entries.
+  return Promise.all([promise1, promise2]);
+}, 'Multiple PerformanceObservers with buffered flag see all entries');
diff --git a/testing/web-platform/tests/performance-timeline/observer-buffered-false.any.js b/testing/web-platform/tests/performance-timeline/observer-buffered-false.any.js
new file mode 100644
index 0000000000..a28100b0fd
--- /dev/null
+++ b/testing/web-platform/tests/performance-timeline/observer-buffered-false.any.js
@@ -0,0 +1,12 @@
+async_test(t => {
+  performance.mark('foo');
+  // Use a timeout to ensure the remainder of the test runs after the entry is created.
+  t.step_timeout(() => {
+    // Observer with buffered flag set to false should not see entry.
+    new PerformanceObserver(() => {
+      assert_unreached('Should not have observed any entry!');
+    }).observe({type: 'mark', buffered: false});
+    // Use a timeout to give time to the observer.
+    t.step_timeout(t.step_func_done(() => {}), 100);
+  }, 0);
+}, 'PerformanceObserver without buffered flag set to false cannot see past entries.');
diff --git a/testing/web-platform/tests/performance-timeline/po-disconnect-removes-observed-types.any.js b/testing/web-platform/tests/performance-timeline/po-disconnect-removes-observed-types.any.js
new file mode 100644
index 0000000000..cac97bea07
--- /dev/null
+++ b/testing/web-platform/tests/performance-timeline/po-disconnect-removes-observed-types.any.js
@@ -0,0 +1,19 @@
+// META: script=performanceobservers.js
+
+async_test(function (t) {
+  const observer  = new PerformanceObserver(
+      t.step_func(function (entryList) {
+        // There should be no mark entry.
+        checkEntries(entryList.getEntries(),
+          [{ entryType: "measure", name: "b"}]);
+        t.done();
+      })
+    );
+  observer.observe({type: "mark"});
+  // Disconnect the observer.
+  observer.disconnect();
+  // Now, only observe measure.
+  observer.observe({type: "measure"});
+  performance.mark("a");
+  performance.measure("b");
+}, "Types observed are forgotten when disconnect() is called.");
diff --git a/testing/web-platform/tests/performance-timeline/po-observe-repeated-type.any.js b/testing/web-platform/tests/performance-timeline/po-observe-repeated-type.any.js
new file mode 100644
index 0000000000..2bba396a6b
--- /dev/null
+++ b/testing/web-platform/tests/performance-timeline/po-observe-repeated-type.any.js
@@ -0,0 +1,17 @@
+// META: script=performanceobservers.js
+
+async_test(function (t) {
+  const observer  = new PerformanceObserver(
+      t.step_func(function (entryList) {
+        checkEntries(entryList.getEntries(),
+          [{ entryType: "mark", name: "early"}]);
+        observer.disconnect();
+        t.done();
+      })
+    );
+  performance.mark("early");
+  // This call will not trigger anything.
+  observer.observe({type: "mark"});
+  // This call should override the previous call and detect the early mark.
+  observer.observe({type: "mark", buffered: true});
+}, "Two calls of observe() with the same 'type' cause override.");
diff --git a/testing/web-platform/tests/resource-timing/buffered-flag.any.js b/testing/web-platform/tests/resource-timing/buffered-flag.any.js
new file mode 100644
index 0000000000..63a386159f
--- /dev/null
+++ b/testing/web-platform/tests/resource-timing/buffered-flag.any.js
@@ -0,0 +1,18 @@
+async_test(t => {
+  performance.clearResourceTimings();
+  // First observer creates second in callback to ensure the entry has been dispatched by the time
+  // the second observer begins observing.
+  new PerformanceObserver(() => {
+    // Second observer requires 'buffered: true' to see an entry.
+    new PerformanceObserver(t.step_func_done(list => {
+      const entries = list.getEntries();
+      assert_equals(entries.length, 1, 'There should be 1 resource entry.');
+      assert_equals(entries[0].entryType, 'resource');
+      assert_greater_than(entries[0].startTime, 0);
+      assert_greater_than(entries[0].responseEnd, entries[0].startTime);
+      assert_greater_than(entries[0].duration, 0);
+      assert_true(entries[0].name.endsWith('resources/empty.js'));
+    })).observe({'type': 'resource', buffered: true});
+  }).observe({'entryTypes': ['resource']});
+  fetch('resources/empty.js');
+}, 'PerformanceObserver with buffered flag sees previous resource entries.');
\ No newline at end of file
diff --git a/testing/web-platform/tests/user-timing/buffered-flag.any.js b/testing/web-platform/tests/user-timing/buffered-flag.any.js
new file mode 100644
index 0000000000..f938c8522d
--- /dev/null
+++ b/testing/web-platform/tests/user-timing/buffered-flag.any.js
@@ -0,0 +1,27 @@
+async_test(t => {
+  // First observer creates second in callback to ensure the entry has been dispatched by the time
+  // the second observer begins observing.
+  new PerformanceObserver(() => {
+    // Second observer requires 'buffered: true' to see an entry.
+    new PerformanceObserver(t.step_func_done(list => {
+      const entries = list.getEntries();
+      assert_equals(entries.length, 1, 'There should be 1 mark entry.');
+      assert_equals(entries[0].entryType, 'mark');
+    })).observe({type: 'mark', buffered: true});
+  }).observe({entryTypes: ['mark']});
+  performance.mark('foo');
+}, 'PerformanceObserver with buffered flag sees previous marks');
+
+async_test(t => {
+  // First observer creates second in callback to ensure the entry has been dispatched by the time
+  // the second observer begins observing.
+  new PerformanceObserver(() => {
+    // Second observer requires 'buffered: true' to see an entry.
+    new PerformanceObserver(t.step_func_done(list => {
+      const entries = list.getEntries();
+      assert_equals(entries.length, 1, 'There should be 1 measure entry.');
+      assert_equals(entries[0].entryType, 'measure');
+    })).observe({type: 'measure', buffered: true});
+  }).observe({entryTypes: ['measure']});
+  performance.measure('bar');
+}, 'PerformanceObserver with buffered flag sees previous measures');