The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/35805e90395c7e4352c313247e5fd38c8ed3c94c

commit 35805e90395c7e4352c313247e5fd38c8ed3c94c
Author: robliao <robliao@chromium.org>
Date: Mon Feb 27 02:41:56 2017

Remove SingleThreadTaskRunner Dependency from TaskSchedulerWorkerPoolHistogramTest.NumTasksBeforeDetach

SchedulerWorkerPoolImpl will have its SingleThreadTaskRunner support
removed.

BUG= 694823 

Review-Url: https://codereview.chromium.org/2712003002
Cr-Commit-Position: refs/heads/master@{#453138}

[modify] https://crrev.com/35805e90395c7e4352c313247e5fd38c8ed3c94c/base/task_scheduler/scheduler_worker_pool_impl_unittest.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/fc203f52e046a8d82e053525d764671f7128f3d4

commit fc203f52e046a8d82e053525d764671f7128f3d4
Author: robliao <robliao@chromium.org>
Date: Mon Feb 27 06:47:16 2017

Introduce SchedulerSingleThreadTaskRunnerManager

This component provides one dedicated thread per
SingleThreadTaskRunner.

Reference Change:
https://codereview.chromium.org/2686593003/

BUG= 684080 ,  694823 

Review-Url: https://codereview.chromium.org/2698843006
Cr-Commit-Position: refs/heads/master@{#453162}

[modify] https://crrev.com/fc203f52e046a8d82e053525d764671f7128f3d4/base/BUILD.gn
[add] https://crrev.com/fc203f52e046a8d82e053525d764671f7128f3d4/base/task_scheduler/scheduler_single_thread_task_runner_manager.cc
[add] https://crrev.com/fc203f52e046a8d82e053525d764671f7128f3d4/base/task_scheduler/scheduler_single_thread_task_runner_manager.h
[add] https://crrev.com/fc203f52e046a8d82e053525d764671f7128f3d4/base/task_scheduler/scheduler_single_thread_task_runner_manager_unittest.cc
[modify] https://crrev.com/fc203f52e046a8d82e053525d764671f7128f3d4/base/task_scheduler/scheduler_worker_pool_impl.cc
[modify] https://crrev.com/fc203f52e046a8d82e053525d764671f7128f3d4/base/task_scheduler/scheduler_worker_pool_params.cc
[modify] https://crrev.com/fc203f52e046a8d82e053525d764671f7128f3d4/base/task_scheduler/scheduler_worker_pool_params.h
[modify] https://crrev.com/fc203f52e046a8d82e053525d764671f7128f3d4/base/task_scheduler/task_scheduler_impl_unittest.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/78d29d2505c18c37f2869bcca08cf18701892655

commit 78d29d2505c18c37f2869bcca08cf18701892655
Author: twellington <twellington@chromium.org>
Date: Thu Mar 02 19:45:23 2017

Revert of Introduce SchedulerSingleThreadTaskRunnerManager (patchset #7 id:280001 of https://codereview.chromium.org/2698843006/ )

Reason for revert:
TaskSchedulerSingleThreadTaskRunnerManagerTest.PrioritySetCorrectly is failing on numerous bots. See  crbug.com/697697 

Original issue's description:
> Introduce SchedulerSingleThreadTaskRunnerManager
>
> This component provides one dedicated thread per
> SingleThreadTaskRunner.
>
> Reference Change:
> https://codereview.chromium.org/2686593003/
>
> BUG= 684080 ,  694823 
>
> Review-Url: https://codereview.chromium.org/2698843006
> Cr-Commit-Position: refs/heads/master@{#453162}
> Committed: https://chromium.googlesource.com/chromium/src/+/fc203f52e046a8d82e053525d764671f7128f3d4

TBR=gab@chromium.org,fdoray@chromium.org,robliao@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG= 684080 ,  694823 ,  697697 

Review-Url: https://codereview.chromium.org/2722113006
Cr-Commit-Position: refs/heads/master@{#454346}

[modify] https://crrev.com/78d29d2505c18c37f2869bcca08cf18701892655/base/BUILD.gn
[delete] https://crrev.com/8dd0cb3cdf573d6ea0021f2962ef8116c9e80857/base/task_scheduler/scheduler_single_thread_task_runner_manager.cc
[delete] https://crrev.com/8dd0cb3cdf573d6ea0021f2962ef8116c9e80857/base/task_scheduler/scheduler_single_thread_task_runner_manager.h
[delete] https://crrev.com/8dd0cb3cdf573d6ea0021f2962ef8116c9e80857/base/task_scheduler/scheduler_single_thread_task_runner_manager_unittest.cc
[modify] https://crrev.com/78d29d2505c18c37f2869bcca08cf18701892655/base/task_scheduler/scheduler_worker_pool_impl.cc
[modify] https://crrev.com/78d29d2505c18c37f2869bcca08cf18701892655/base/task_scheduler/scheduler_worker_pool_params.cc
[modify] https://crrev.com/78d29d2505c18c37f2869bcca08cf18701892655/base/task_scheduler/scheduler_worker_pool_params.h
[modify] https://crrev.com/78d29d2505c18c37f2869bcca08cf18701892655/base/task_scheduler/task_scheduler_impl_unittest.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/cee951ecb8aff83a6eb0ff734241813f735e8c45

commit cee951ecb8aff83a6eb0ff734241813f735e8c45
Author: robliao <robliao@chromium.org>
Date: Fri Mar 10 20:21:29 2017

Introduce SchedulerSingleThreadTaskRunnerManager

This component provides one dedicated thread per
SingleThreadTaskRunner.

Reference Change:
https://codereview.chromium.org/2686593003/

BUG= 684080 ,  694823 ,  697697 

Review-Url: https://codereview.chromium.org/2698843006
Cr-Original-Commit-Position: refs/heads/master@{#453162}
Committed: https://chromium.googlesource.com/chromium/src/+/fc203f52e046a8d82e053525d764671f7128f3d4
Review-Url: https://codereview.chromium.org/2698843006
Cr-Commit-Position: refs/heads/master@{#456148}

[modify] https://crrev.com/cee951ecb8aff83a6eb0ff734241813f735e8c45/base/BUILD.gn
[add] https://crrev.com/cee951ecb8aff83a6eb0ff734241813f735e8c45/base/task_scheduler/scheduler_single_thread_task_runner_manager.cc
[add] https://crrev.com/cee951ecb8aff83a6eb0ff734241813f735e8c45/base/task_scheduler/scheduler_single_thread_task_runner_manager.h
[add] https://crrev.com/cee951ecb8aff83a6eb0ff734241813f735e8c45/base/task_scheduler/scheduler_single_thread_task_runner_manager_unittest.cc
[modify] https://crrev.com/cee951ecb8aff83a6eb0ff734241813f735e8c45/base/task_scheduler/scheduler_worker.cc
[modify] https://crrev.com/cee951ecb8aff83a6eb0ff734241813f735e8c45/base/task_scheduler/scheduler_worker.h
[modify] https://crrev.com/cee951ecb8aff83a6eb0ff734241813f735e8c45/base/task_scheduler/scheduler_worker_pool_impl.cc
[modify] https://crrev.com/cee951ecb8aff83a6eb0ff734241813f735e8c45/base/task_scheduler/scheduler_worker_pool_params.cc
[modify] https://crrev.com/cee951ecb8aff83a6eb0ff734241813f735e8c45/base/task_scheduler/scheduler_worker_pool_params.h
[modify] https://crrev.com/cee951ecb8aff83a6eb0ff734241813f735e8c45/base/task_scheduler/task_scheduler_impl_unittest.cc

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/94b6750c5377b3e4079ea0d74fbbb0e8912df346

commit 94b6750c5377b3e4079ea0d74fbbb0e8912df346
Author: robliao <robliao@chromium.org>
Date: Wed Mar 15 17:40:46 2017

Remove SingleThreadTaskRunner Support from SchedulerWorkerPoolImpl

With SchedulerSingleThreadTaskRunnerManager, SchedulerWorkerPoolImpl
no longer needs to handle SingleThreadTaskRunners.

BUG= 694823 

Review-Url: https://codereview.chromium.org/2721553003
Cr-Commit-Position: refs/heads/master@{#457124}

[modify] https://crrev.com/94b6750c5377b3e4079ea0d74fbbb0e8912df346/base/task_scheduler/priority_queue.cc
[modify] https://crrev.com/94b6750c5377b3e4079ea0d74fbbb0e8912df346/base/task_scheduler/priority_queue.h
[modify] https://crrev.com/94b6750c5377b3e4079ea0d74fbbb0e8912df346/base/task_scheduler/priority_queue_unittest.cc
[modify] https://crrev.com/94b6750c5377b3e4079ea0d74fbbb0e8912df346/base/task_scheduler/scheduler_worker_pool.h
[modify] https://crrev.com/94b6750c5377b3e4079ea0d74fbbb0e8912df346/base/task_scheduler/scheduler_worker_pool_impl.cc
[modify] https://crrev.com/94b6750c5377b3e4079ea0d74fbbb0e8912df346/base/task_scheduler/scheduler_worker_pool_impl.h
[modify] https://crrev.com/94b6750c5377b3e4079ea0d74fbbb0e8912df346/base/task_scheduler/scheduler_worker_pool_impl_unittest.cc
[modify] https://crrev.com/94b6750c5377b3e4079ea0d74fbbb0e8912df346/base/task_scheduler/task_scheduler_impl.cc

Did a quick once over and I think we've got the most obvious cases here. If there are more, then we can remove those when we find them.