Fix flakiness in MultithreadedMetrics test for single sample metrics.

Fix flakiness in MultithreadedMetrics test for single sample metrics.

Metric shutdown ends up posting a few tasks for which our simple
DoNothing trampoline was insufficient to ensure they completed.
Instead shutdown the thread since we don't need it anymore anyways;
this waits for all posted tasks to complete.

BUG=718973
TEST=ran android test 25 times without failure, failed immediately
prior to this fix.

Review-Url: https://codereview.chromium.org/2894553004
Cr-Commit-Position: refs/heads/master@{#473023}
Committed: https://chromium.googlesource.com/chromium/src/+/a692b66c652e1e0fd2446f469093ee3e5d81539d

[DaleCurtis, 2017-05-18 23:57:00]

dalecurtis@chromium.org changed reviewers:
+ isheriff@chromium.org

[DaleCurtis, 2017-05-18 23:57:04]

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

[DaleCurtis, 2017-05-18 23:57:31]

dalecurtis@chromium.org changed reviewers:
+ isherman@chromium.org
- isheriff@chromium.org

[DaleCurtis, 2017-05-18 23:57:32]

Whoops, -isheriff, meant isherman. Sorry!

[commit-bot: I haz the power, 2017-05-18 23:58:46]

Dry run: CQ is trying da patch.

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

[Ilya Sherman, 2017-05-19 00:12:41]

https://codereview.chromium.org/2894553004/diff/1/components/metrics/single_s...
File components/metrics/single_sample_metrics_factory_impl_unittest.cc (right):

https://codereview.chromium.org/2894553004/diff/1/components/metrics/single_s...
components/metrics/single_sample_metrics_factory_impl_unittest.cc:50:
thread_.Stop();
I'm honestly a bit confused: I'd expect PostTask() followed immediately by
Stop() to lose the posted task.  Is there not any need to wait for the task to
execute?

[DaleCurtis, 2017-05-19 00:13:29]

https://codereview.chromium.org/2894553004/diff/1/components/metrics/single_s...
File components/metrics/single_sample_metrics_factory_impl_unittest.cc (right):

https://codereview.chromium.org/2894553004/diff/1/components/metrics/single_s...
components/metrics/single_sample_metrics_factory_impl_unittest.cc:50:
thread_.Stop();
On 2017/05/19 at 00:12:41, Ilya Sherman wrote:
> I'm honestly a bit confused: I'd expect PostTask() followed immediately by
Stop() to lose the posted task.  Is there not any need to wait for the task to
execute?

Thread::Stop() joins, so all posted tasks are waited for.

[Ilya Sherman, 2017-05-19 00:18:55]

https://codereview.chromium.org/2894553004/diff/1/components/metrics/single_s...
File components/metrics/single_sample_metrics_factory_impl_unittest.cc (right):

https://codereview.chromium.org/2894553004/diff/1/components/metrics/single_s...
components/metrics/single_sample_metrics_factory_impl_unittest.cc:50:
thread_.Stop();
On 2017/05/19 00:13:29, DaleCurtis_OOO_May_5_To_May23 wrote:
> On 2017/05/19 at 00:12:41, Ilya Sherman wrote:
> > I'm honestly a bit confused: I'd expect PostTask() followed immediately by
> Stop() to lose the posted task.  Is there not any need to wait for the task to
> execute?
> 
> Thread::Stop() joins, so all posted tasks are waited for.

Ah, great! =)  LGTM in that case -- thanks!

[DaleCurtis, 2017-05-19 00:19:23]

The CQ bit was unchecked by dalecurtis@chromium.org

[DaleCurtis, 2017-05-19 00:19:25]

The CQ bit was checked by dalecurtis@chromium.org

[commit-bot: I haz the power, 2017-05-19 00:19:50]

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, 2017-05-19 01:42:55]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1495153165269770, "parent_rev":
"f4938cd4dbf88834816a592abeec512d240883d5", "commit_rev":
"a692b66c652e1e0fd2446f469093ee3e5d81539d"}

[commit-bot: I haz the power, 2017-05-19 01:43:03]

Description was changed from

==========
Fix flakiness in MultithreadedMetrics test for single sample metrics.

Metric shutdown ends up posting a few tasks for which our simple
DoNothing trampoline was insufficient to ensure they completed.
Instead shutdown the thread since we don't need it anymore anyways;
this waits for all posted tasks to complete.

BUG=718973
TEST=ran android test 25 times without failure, failed immediately
prior to this fix.
==========

to

==========
Fix flakiness in MultithreadedMetrics test for single sample metrics.

Metric shutdown ends up posting a few tasks for which our simple
DoNothing trampoline was insufficient to ensure they completed.
Instead shutdown the thread since we don't need it anymore anyways;
this waits for all posted tasks to complete.

BUG=718973
TEST=ran android test 25 times without failure, failed immediately
prior to this fix.

Review-Url: https://codereview.chromium.org/2894553004
Cr-Commit-Position: refs/heads/master@{#473023}
Committed:
https://chromium.googlesource.com/chromium/src/+/a692b66c652e1e0fd2446f469093...
==========

[commit-bot: I haz the power, 2017-05-19 01:43:04]

Committed patchset #1 (id:1) as
https://chromium.googlesource.com/chromium/src/+/a692b66c652e1e0fd2446f469093...