This will be used by Chromium to check for interface blocks mismatches.

BUG=621031

Change-Id: Ia6cc19e5d7b2a5c33af558d65b87885a6b72cea3
Reviewed-on: https://chromium-review.googlesource.com/359607Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Commit-Queue: Corentin Wallez <cwallez@chromium.org>