GitLab

This adds comments to experiment_status.proto and
experiments_specifics.proto explaining why these deprecated definitions
can't be removed yet.

Bug: 1009361
Change-Id: Id2519a51d9c66a569015be7a58580b2299fe852b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2032111
Auto-Submit: Marc Treib <treib@chromium.org>
Reviewed-by: Tim Schumann <tschumann@chromium.org>
Commit-Queue: Tim Schumann <tschumann@chromium.org>
Cr-Commit-Position: refs/heads/master@{#737294}