Add EXPECT_SAME_FILE functionality to find_unittests.
Add EXPECT_SAME_FILE functionality to find_unittests.

This allows us to validate whether 2 paths refer to the same physical file, whereas simply doing a case insensitive path comparison may fail if the paths are sufficiently convoluted.
Review URL: http://codereview.appspot.com/5285041

git-svn-id: db59699583a60be9a535cd09cdc9132301867226@461 15e8cca8-e42c-11de-a347-f34a4f72eb7d

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