GitLab

Now it registers thread as a sequence and accepts MessagePump
as a constructor argument.

Bug: 828835
Change-Id: Ibbfd674a5c7f739e30baaa8a026e30827d521a87
Reviewed-on: https://chromium-review.googlesource.com/1167482Reviewed-by: Alex Clarke <alexclarke@chromium.org>
Commit-Queue: Greg Kraynov <kraynov@chromium.org>
Cr-Commit-Position: refs/heads/master@{#581835}