Summary: When the main file is created from a membuffer, there is no file entry that can be retrieved. This uses "__GLOBAL_I_a" in that case which is what was always used before r208128.
Reviewers: majnemer, thakis
Reviewed By: thakis
Subscribers: yaron.keren, rsmith, cfe-commits
Differential Revision: http://reviews.llvm.org/D5043
llvm-svn: 216495
