Adding test to avoid memory leak when autoplayed video never become visible

Adding test to avoid memory leak when autoplayed video never become visible

BUG=627539
Committed: https://crrev.com/339881fcea518c6f7ff6e1a04a2a5f40e26de850
Cr-Commit-Position: refs/heads/master@{#412210}

[Zhiqiang Zhang (Slow), 2016-08-15 20:13:32]

zqzhang@chromium.org changed reviewers:
+ mlamouri@chromium.org

[Zhiqiang Zhang (Slow), 2016-08-15 20:13:33]

PTAL.

I tried the leak on trunk today. It seems the flaky leak is much less like to
trigger. Don't know why.

Tried this test 40 times and no leak was detected.

[mlamouri (slow - plz ping), 2016-08-16 09:07:13]

lgtm

Is the leak fixed then?

[Zhiqiang Zhang (Slow), 2016-08-16 09:33:55]

On 2016/08/16 09:07:13, Mounir Lamouri wrote:
> lgtm
> 
> Is the leak fixed then?

The leak seems to be super hard to trigger now.

It only happens when I comment out `m_autoplayVisibilityObserver->stop()` in
HTMLMediaElement, and run `autoplay-muted` tests.
I narrowed down `autoplay-muted` tests and found that 3 of
async_test/promise_test can trigger the leak when they are run at the same time,
and one test that should have failed due to commenting `stop()` does not fail.

So my guess is that there exist some races among the async_tests/promise_tests
that caused the leak. This might also explain why the leak is flaky.

[Zhiqiang Zhang (Slow), 2016-08-16 09:34:14]

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

[commit-bot: I haz the power, 2016-08-16 09:34:32]

Dry run: 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, 2016-08-16 10:52:20]

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

[commit-bot: I haz the power, 2016-08-16 10:52:21]

Dry run: This issue passed the CQ dry run.

[Zhiqiang Zhang (Slow), 2016-08-16 10:53:27]

The CQ bit was checked by zqzhang@chromium.org

[commit-bot: I haz the power, 2016-08-16 10:53:45]

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, 2016-08-16 10:57:13]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2016-08-16 10:58:40]

Description was changed from

==========
Adding test to avoid memory leak when autoplayed video never become visible

BUG=627539
==========

to

==========
Adding test to avoid memory leak when autoplayed video never become visible

BUG=627539

Committed: https://crrev.com/339881fcea518c6f7ff6e1a04a2a5f40e26de850
Cr-Commit-Position: refs/heads/master@{#412210}
==========

[commit-bot: I haz the power, 2016-08-16 10:58:41]

Patchset 2 (id:??) landed as
https://crrev.com/339881fcea518c6f7ff6e1a04a2a5f40e26de850
Cr-Commit-Position: refs/heads/master@{#412210}