This will be useful for tools like the recipe autoroller to
semi-intelligently choose a collection of reviewers.

Bug:

Change-Id: I7a238127e126340c033fc8e80523ef2408ebf970
Reviewed-on: https://chromium-review.googlesource.com/479679
Commit-Queue: Andrii Shyshkalov <tandrii@chromium.org>
Reviewed-by: Andrii Shyshkalov <tandrii@chromium.org>