GitLab

Give an indication in the documentation where this structure is
defined/specified. So others readers studing this code can read
more information about it.

BUG=None

Change-Id: Iedf747d27231be4982010519365a6caa6dfc1c6d
Reviewed-on: https://chromium-review.googlesource.com/518046
Commit-Queue: Thiago Farina <tfarina@chromium.org>
Reviewed-by: Eric Roman <eroman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#475766}