GitLab

This CL adds feature param to control default pin state for the
experiment.

Change-Id: I42f8244adfc5f8fb5a195f7a5243314864cd57a8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2488721Reviewed-by: Tommy Steimel <steimel@chromium.org>
Reviewed-by: Becca Hughes <beccahughes@chromium.org>
Reviewed-by: Tetsui Ohkubo <tetsui@chromium.org>
Commit-Queue: Jazz Xu <jazzhsu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#820471}