Allow referencing buganizer issues with ANGLE CLs. Based on http://google3/experimental/users/jsharkey/gitwatcher2/configs.py?l=42&rcl=299145346, chromium CLs with b: should be found by buganizer. BUG=b:151095080 Change-Id: Iaf4def18dbe52fe87c9e4655f114fac225d429ce Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2095595 Commit-Queue: Geoff Lang <geofflang@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org>