GitLab

I anticipate needing it for notifications for lacros. See
go/lacros and go/lacros-notifications.

Also, clean up BUILD.gn slightly -- enable_native_notifications is
always true on Chrome OS.

Bug: 1113889
Change-Id: I6c3bc7f81f81157568f8c1b2969f98a82a037b6d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2339450
Commit-Queue: Jun Mukai <mukai@chromium.org>
Auto-Submit: James Cook <jamescook@chromium.org>
Reviewed-by: Jun Mukai <mukai@chromium.org>
Cr-Commit-Position: refs/heads/master@{#795968}