Use absolute paths in angle_perftests.gypi Otherwise in the Chromium build gyp might have a wrong cwd and then ninja will fail to find the files to compile. BUG=angleproject:892 Change-Id: I6b7beef5ecad62cc345b49253cedbde0ac166c17 Reviewed-on: https://chromium-review.googlesource.com/273161 Reviewed-by: Jamie Madill <jmadill@chromium.org> Tested-by: Jamie Madill <jmadill@chromium.org>