[scheduler] Make any thread lock in TaskQueueImpl reentrable.

[scheduler] Make any thread lock in TaskQueueImpl reentrable.

This solves a long-standing problem of not being able to call
TaskQueueImpl::HasPendingImmediateWork safely inside
OnTimeDomainHasImmediateWork.

Making the lock reentrable from main thread will allow main-thread only
scheduling logic to call to TaskQueueImpl::HasPendingImmediateWork
safely.

R=skyostil@chromium.org,alexclarke@chromium.org
BUG=699541

[altimin, 2017-03-29 17:08:18]

PTAL

[altimin, 2017-03-29 17:09:52]

The CQ bit was checked by altimin@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2017-03-29 17:10:35]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[Sami, 2017-03-29 17:23:25]

Hmm, I think recursive locks aren't supported in Chrome for a good reason since
they tend to be used to paper over unclear interfaces between or within
components. I wonder if there's way to refactor things so that this isn't
needed? For instance maybe OnTimeDomainHasImmediateWork could be changed to pass
in the necessary data directly?

[commit-bot: I haz the power, 2017-03-29 19:27:07]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2017-03-29 19:27:08]

Dry run: This issue passed the CQ dry run.

[altimin, 2017-03-30 16:47:01]

Description was changed from

==========
[scheduler] Make any thread lock in TaskQueueImpl reentrable.

This solves a long-standing problem of not being able to call
TaskQueueImpl::HasPendingImmediateWork safely inside
OnTimeDomainHasImmediateWork.

Making the lock reentrable from main thread will allow main-thread only
scheduling logic to call to TaskQueueImpl::HasPendingImmediateWork
safely.

R=skyostil@chromium.org,alexclarke@chromium.org
BUG=699541
==========

to

==========
[scheduler] Make any thread lock in TaskQueueImpl reentrable.

This solves a long-standing problem of not being able to call
TaskQueueImpl::HasPendingImmediateWork safely inside
OnTimeDomainHasImmediateWork.

Making the lock reentrable from main thread will allow main-thread only
scheduling logic to call to TaskQueueImpl::HasPendingImmediateWork
safely.

R=skyostil@chromium.org,alexclarke@chromium.org
BUG=699541
==========

[altimin, 2017-03-30 16:47:23]

Decided that we don't want reentrable locks.