Move MessageLoop::current() to MessageLoopCurrent::Get().

Follow-up to https://chromium-review.googlesource.com/c/chromium/src/+/957760
this will allow migrating the majority of callers of
MessageLoop::current() to not even have to use message_loop.h :).

R=thestig@chromium.org

Bug: 825327
Change-Id: Idfca0575c363463442225a46dbadfc202aab4669
Reviewed-on: https://chromium-review.googlesource.com/1008265
Commit-Queue: Gabriel Charette <gab@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Cr-Commit-Position: refs/heads/master@{#550875}

CrOS-Libchrome-Original-Commit: e6bea7b2e8d3281f13a826645941f52b037c10a0
4 files changed
tree: b49591d16c039c69c961af61b8b1b141e6942cc8
  1. base/
  2. build/
  3. components/
  4. dbus/
  5. device/
  6. ipc/
  7. mojo/
  8. testing/
  9. third_party/
  10. ui/