[MessageLoop cleanup] Remove unused MessageLoopCurrent::QuitWhenIdleClosure method

I realized @ https://chromium-review.googlesource.com/c/chromium/src/+/1055729/1/PRESUBMIT.py#416
that I should really complete the migration off
MessageLoop::QuitWhenIdleClosure and then further realized it should
really be coalesced with similar RunLoop helpers (already covered in
presubmit by "RunLoop::QuitCurrent*").
This is the last CL to make that so.

R=danakj@chromium.org, dpranke@chromium.org, kylechar@chromium.org

Bug: 825327
Change-Id: Id0fa7ca441b60e90b4ebadfa7fc705690a4aecba
Reviewed-on: https://chromium-review.googlesource.com/1055891
Commit-Queue: Gabriel Charette <gab@chromium.org>
Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Reviewed-by: kylechar <kylechar@chromium.org>
Reviewed-by: danakj <danakj@chromium.org>
Cr-Commit-Position: refs/heads/master@{#559914}

CrOS-Libchrome-Original-Commit: 5110d6ba39549b71be178fb0e72b0577e9cfa716
2 files changed
tree: a5ff8416e5b49a474cc815eb7fd178180f046f0b
  1. base/
  2. build/
  3. components/
  4. dbus/
  5. device/
  6. ipc/
  7. mojo/
  8. testing/
  9. third_party/
  10. ui/