The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/1af04705b43547c1b6fef0080c092aae06b1dca8

commit 1af04705b43547c1b6fef0080c092aae06b1dca8
Author: robliao <robliao@chromium.org>
Date: Mon Mar 20 23:26:41 2017

Add WaitForWork to SchedulerWorker::Delegate

This will allow the COM delegate to wait on both the Windows message
queue and the SchedulerWorker WakeUp event a la
MsgWaitForMultipleObjects.

Reference Changelist:
https://codereview.chromium.org/2762703002

BUG= 662122 

Review-Url: https://codereview.chromium.org/2759203002
Cr-Commit-Position: refs/heads/master@{#458233}

[modify] https://crrev.com/1af04705b43547c1b6fef0080c092aae06b1dca8/base/task_scheduler/scheduler_worker.cc
[modify] https://crrev.com/1af04705b43547c1b6fef0080c092aae06b1dca8/base/task_scheduler/scheduler_worker.h

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/80891393a521ee82efb1d9c513e540baa270dd02

commit 80891393a521ee82efb1d9c513e540baa270dd02
Author: robliao <robliao@chromium.org>
Date: Wed Mar 22 22:30:15 2017

Add the COM STA Task Runner

The COM STA Task Runner executes tasks in a COM STA. Task runners in
the future may share STAs, so callers should not assume STAs are shared
or are dedicated.

Callers requiring tasks to run in the same STA should post to the same
task runner.

BUG= 662122 

Review-Url: https://codereview.chromium.org/2765703002
Cr-Commit-Position: refs/heads/master@{#458900}

[modify] https://crrev.com/80891393a521ee82efb1d9c513e540baa270dd02/base/task_scheduler/scheduler_single_thread_task_runner_manager.cc
[modify] https://crrev.com/80891393a521ee82efb1d9c513e540baa270dd02/base/task_scheduler/scheduler_single_thread_task_runner_manager.h
[modify] https://crrev.com/80891393a521ee82efb1d9c513e540baa270dd02/base/task_scheduler/scheduler_single_thread_task_runner_manager_unittest.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/75dd50b325a709221dd971e61eb3e6f53de1a8aa

commit 75dd50b325a709221dd971e61eb3e6f53de1a8aa
Author: robliao <robliao@chromium.org>
Date: Wed Mar 29 17:11:17 2017

Add Support to Get a COM STA Task Runner from the Task Scheduler API

This also adds support for COM STA Task Runner for TaskSchedulerImpl as
well as ScopedTaskScheduler.

BUG= 662122 

Review-Url: https://codereview.chromium.org/2768873007
Cr-Commit-Position: refs/heads/master@{#460430}

[modify] https://crrev.com/75dd50b325a709221dd971e61eb3e6f53de1a8aa/base/task_scheduler/post_task.cc
[modify] https://crrev.com/75dd50b325a709221dd971e61eb3e6f53de1a8aa/base/task_scheduler/post_task.h
[modify] https://crrev.com/75dd50b325a709221dd971e61eb3e6f53de1a8aa/base/task_scheduler/task_scheduler.h
[modify] https://crrev.com/75dd50b325a709221dd971e61eb3e6f53de1a8aa/base/task_scheduler/task_scheduler_impl.cc
[modify] https://crrev.com/75dd50b325a709221dd971e61eb3e6f53de1a8aa/base/task_scheduler/task_scheduler_impl.h
[modify] https://crrev.com/75dd50b325a709221dd971e61eb3e6f53de1a8aa/base/task_scheduler/task_scheduler_impl_unittest.cc
[modify] https://crrev.com/75dd50b325a709221dd971e61eb3e6f53de1a8aa/base/test/scoped_task_scheduler.cc
[modify] https://crrev.com/75dd50b325a709221dd971e61eb3e6f53de1a8aa/base/test/scoped_task_scheduler.h
[modify] https://crrev.com/75dd50b325a709221dd971e61eb3e6f53de1a8aa/base/test/scoped_task_scheduler_unittest.cc

Can you open a bug to get rid of SchedulerBackwardCompatibility::INIT_COM_STA usage now (especially outside of redirection use cases -- e.g. I'm thinking of the recent addition to service process which would be better served by an explicit STATaskRunner request from the printing code).

Done: http://crbug.com/706512