Add clang-format integration for 'git cl format'. This will allow us to eventually make a presubmit script for ANGLE, and also will help new contributors who aren't as familiar with the style guide. One outstanding issue is the lack of proper breaking before array initializers. We don't use arrays all over the place, but this will likely require a patch for clang. BUG=angleproject:762 Change-Id: I4702b1fcdfa10b7682b07316be59ec67bcf84943 Reviewed-on: https://chromium-review.googlesource.com/285901 Reviewed-by: Geoff Lang <geofflang@chromium.org> Reviewed-by: Zhenyao Mo <zmo@chromium.org> Tested-by: Jamie Madill <jmadill@chromium.org>