GitLab

This is a precursor for an upcoming change that will split the public bits
of the MessageLoop class (used through MessageLoop(ForUI|IO)::current())
to another class.

Bug: 825327
Change-Id: I3cda2a0e1b2ff48aaeeaeeb68d99c5dda926350f
Reviewed-on: https://chromium-review.googlesource.com/978776
Commit-Queue: Gabriel Charette <gab@chromium.org>
Reviewed-by: kylechar <kylechar@chromium.org>
Reviewed-by: danakj <danakj@chromium.org>
Cr-Commit-Position: refs/heads/master@{#548109}