GitLab

Adding basic UI elements as outlined in the PRD attached to the bug.
Note that these are not final, or to spec (as no spec exists yet),
and it is all behind an experimental flag.

Bug:1016193

CQ-DEPEND=CL:2079711

Change-Id: I6ec7fee8247342688d883e7ad6d0c6a05940cb25
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2079718
Commit-Queue: Daniel Ng <danielng@google.com>
Reviewed-by: Tommy Li <tommycli@chromium.org>
Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Reviewed-by: Julian Watson <juwa@google.com>
Cr-Commit-Position: refs/heads/master@{#746251}