Separate the create and start phases in SchedulerSingleThreadTaskRunnerManager.
With this CL, single-thread TaskRunners created from a newly
instantiated SchedulerSingleThreadTaskRunnerManager aren't backed
by a thread (and hence their tasks can't run right away). Thread
creation is delayed until
SchedulerSingleThreadTaskRunnerManager::Start().
BUG=690706
Review-Url: https://codereview.chromium.org/2806413002
Cr-Commit-Position: refs/heads/master@{#465439}
CrOS-Libchrome-Original-Commit: b64df4b2b6feeebc0ae622fb2fc012cfa6b58c1a
10 files changed