Expose QuitWhenIdle via The TimeDomain API

The TimeDomain introduced by http://crrev.com/c/1324391 needs to
know if the current RunLoop should quit when idle because if so
it needs to stop advancing mock time.  We do this by plumbing a flag
through to MaybeFastForwardToNextTask.

Bug: 863341, 891670
Change-Id: I71d8240fa5c6e7088cafacba57a31ec15abfe695
Reviewed-on: https://chromium-review.googlesource.com/c/1337336
Commit-Queue: Alex Clarke <alexclarke@chromium.org>
Reviewed-by: Sami Kyöstilä <skyostil@chromium.org>
Reviewed-by: Gabriel Charette <gab@chromium.org>
Reviewed-by: Alexander Timin <altimin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#609977}
17 files changed