Add third_party/googletest to .gitignore. We now mirror the entire directory. Not just src. Bug: angleproject:3151 Change-Id: Ifdf351f7fe7b227fc58d08ca3472c9adb9bbe5e7 Reviewed-on: https://chromium-review.googlesource.com/c/1487632 Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Jamie Madill <jmadill@chromium.org>