GitLab

They currently target a revised stub interface for CastSocket, but not a full implementation.
That change is witheld in a separate Git client so this CL can remain at a manageable size.

Thanks!
BUG=396345
R=mfoltz@chromium.org
CC=wez@chromium.org

Review URL: https://codereview.chromium.org/555283002

Cr-Commit-Position: refs/heads/master@{#296993}