This gives PRESUBMIT equal support for all the
gerrit-style footers that we're migrating to.

R=iannucci@chromium.org, tandrii@chromium.org

Bug: 710327,710803
Change-Id: I64b8f39ef923d90ebda7dd191b83d1a7cc87c776
Reviewed-on: https://chromium-review.googlesource.com/506551Reviewed-by: Robbie Iannucci <iannucci@chromium.org>
Reviewed-by: Andrii Shyshkalov <tandrii@chromium.org>
Commit-Queue: Aaron Gable <agable@chromium.org>