Fix race condition in TaskSchedulerTaskTrackerTest.WillPostAndRunLongTaskBeforeShutdown.

Fix race condition in TaskSchedulerTaskTrackerTest.WillPostAndRunLongTaskBeforeShutdown.

Previously, when
TaskSchedulerTaskTrackerTest.WillPostAndRunLongTaskBeforeShutdown ran
with param = SKIP_ON_SHUTDOWN, these events could occur:

  Thread    Action
-----------------------------------------------------------------------
1 Main      Create a skip on shutdown task.
2 Main      TaskTracker::WillPostTask()
3 Main      Start thread to run task (SimpleThread::Start).
4 Main      Start thread to call shutdown (SimpleThread::Start).
5 Shutdown  TaskTracker::Shutdown()
              Returns immediately since the SKIP_ON_SHUTDOWN task
              isn't running yet.
6 Main      Expect shutdown to be blocked on the SKIP_ON_SHUTDOWN task.
              Error!

So far, we've been lucky and #5 never ran before the SKIP_ON_SHUTDOWN
had time to start running. However, making SimpleThread::Start()
non-blocking (https://codereview.chromium.org/2664953004) made
this series of events occur a few times on bots.

BUG=

Review-Url: https://codereview.chromium.org/2798373002
Cr-Commit-Position: refs/heads/master@{#462843}
Committed: https://chromium.googlesource.com/chromium/src/+/539e731c557cbce418d3ac1ea315f6cc9bd0e21f

[fdoray, 2017-04-06 17:35:46]

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

[commit-bot: I haz the power, 2017-04-06 17:36:41]

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

[fdoray, 2017-04-06 17:37:00]

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

[commit-bot: I haz the power, 2017-04-06 17:37:40]

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

[fdoray, 2017-04-06 17:38:21]

fdoray@chromium.org changed reviewers:
+ gab@chromium.org, robliao@chromium.org

[fdoray, 2017-04-06 17:38:22]

PTAL

[commit-bot: I haz the power, 2017-04-06 17:52:21]

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

[commit-bot: I haz the power, 2017-04-06 17:52:22]

Dry run: This issue passed the CQ dry run.

[robliao, 2017-04-06 18:26:26]

lgtm + comment

https://codereview.chromium.org/2798373002/diff/20001/base/task_scheduler/tas...
File base/task_scheduler/task_tracker_unittest.cc (right):

https://codereview.chromium.org/2798373002/diff/20001/base/task_scheduler/tas...
base/task_scheduler/task_tracker_unittest.cc:268: WaitableEvent
task_scheduled(WaitableEvent::ResetPolicy::AUTOMATIC,
This might be clearer as task_running.

[gab, 2017-04-06 18:49:11]

lgtm

[fdoray, 2017-04-07 12:23:21]

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

[commit-bot: I haz the power, 2017-04-07 12:23:37]

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

[fdoray, 2017-04-07 12:26:21]

The CQ bit was unchecked by fdoray@chromium.org

[fdoray, 2017-04-07 12:26:28]

https://codereview.chromium.org/2798373002/diff/20001/base/task_scheduler/tas...
File base/task_scheduler/task_tracker_unittest.cc (right):

https://codereview.chromium.org/2798373002/diff/20001/base/task_scheduler/tas...
base/task_scheduler/task_tracker_unittest.cc:268: WaitableEvent
task_scheduled(WaitableEvent::ResetPolicy::AUTOMATIC,
On 2017/04/06 18:26:26, robliao wrote:
> This might be clearer as task_running.

Done.

[fdoray, 2017-04-07 12:26:33]

The CQ bit was checked by fdoray@chromium.org

[fdoray, 2017-04-07 12:26:34]

The patchset sent to the CQ was uploaded after l-g-t-m from
robliao@chromium.org, gab@chromium.org
Link to the patchset: https://codereview.chromium.org/2798373002/#ps40001
(title: "CR-robliao-9")

[commit-bot: I haz the power, 2017-04-07 12:26:50]

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

[commit-bot: I haz the power, 2017-04-07 12:36:25]

CQ is committing da patch.

Bot data: {"patchset_id": 40001, "attempt_start_ts": 1491567993741900,
"parent_rev": "d332296ceffaf87939123159cb58d12dea283c27", "commit_rev":
"539e731c557cbce418d3ac1ea315f6cc9bd0e21f"}

[commit-bot: I haz the power, 2017-04-07 12:37:18]

Description was changed from

==========
Fix race condition in
TaskSchedulerTaskTrackerTest.WillPostAndRunLongTaskBeforeShutdown.

Previously, when
TaskSchedulerTaskTrackerTest.WillPostAndRunLongTaskBeforeShutdown ran
with param = SKIP_ON_SHUTDOWN, these events could occur:

  Thread    Action
-----------------------------------------------------------------------
1 Main      Create a skip on shutdown task.
2 Main      TaskTracker::WillPostTask()
3 Main      Start thread to run task (SimpleThread::Start).
4 Main      Start thread to call shutdown (SimpleThread::Start).
5 Shutdown  TaskTracker::Shutdown()
              Returns immediately since the SKIP_ON_SHUTDOWN task
              isn't running yet.
6 Main      Expect shutdown to be blocked on the SKIP_ON_SHUTDOWN task.
              Error!

So far, we've been lucky and #5 never ran before the SKIP_ON_SHUTDOWN
had time to start running. However, making SimpleThread::Start()
non-blocking (https://codereview.chromium.org/2664953004) made
this series of events occur a few times on bots.

BUG=
==========

to

==========
Fix race condition in
TaskSchedulerTaskTrackerTest.WillPostAndRunLongTaskBeforeShutdown.

Previously, when
TaskSchedulerTaskTrackerTest.WillPostAndRunLongTaskBeforeShutdown ran
with param = SKIP_ON_SHUTDOWN, these events could occur:

  Thread    Action
-----------------------------------------------------------------------
1 Main      Create a skip on shutdown task.
2 Main      TaskTracker::WillPostTask()
3 Main      Start thread to run task (SimpleThread::Start).
4 Main      Start thread to call shutdown (SimpleThread::Start).
5 Shutdown  TaskTracker::Shutdown()
              Returns immediately since the SKIP_ON_SHUTDOWN task
              isn't running yet.
6 Main      Expect shutdown to be blocked on the SKIP_ON_SHUTDOWN task.
              Error!

So far, we've been lucky and #5 never ran before the SKIP_ON_SHUTDOWN
had time to start running. However, making SimpleThread::Start()
non-blocking (https://codereview.chromium.org/2664953004) made
this series of events occur a few times on bots.

BUG=

Review-Url: https://codereview.chromium.org/2798373002
Cr-Commit-Position: refs/heads/master@{#462843}
Committed:
https://chromium.googlesource.com/chromium/src/+/539e731c557cbce418d3ac1ea315...
==========

[commit-bot: I haz the power, 2017-04-07 12:37:19]

Committed patchset #3 (id:40001) as
https://chromium.googlesource.com/chromium/src/+/539e731c557cbce418d3ac1ea315...