Work around GC bug to fix flaky autoplay tests

Work around GC bug to fix flaky autoplay tests

With these changes both tests appear to be reliable.

BUG=357080
BUG=400659
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=179647

[philipj_slow, 2014-08-06 11:36:19]

PTAL

[acolwell GONE FROM CHROMIUM, 2014-08-06 15:52:19]

lgtm

[philipj_slow, 2014-08-06 16:37:55]

The CQ bit was checked by philipj@opera.com

[commit-bot: I haz the power, 2014-08-06 16:38:56]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/philipj@opera.com/441253003/1

[commit-bot: I haz the power, 2014-08-06 17:42:12]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  win_blink_rel on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/win_blink_rel/builds/21392)

[commit-bot: I haz the power, 2014-08-06 18:27:08]

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

[commit-bot: I haz the power, 2014-08-06 18:27:09]

Try jobs failed on following builders:
  win_blink_rel on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/win_blink_rel/builds/21399)

[philipj_slow, 2014-08-06 18:58:25]

The CQ bit was checked by philipj@opera.com

[commit-bot: I haz the power, 2014-08-06 19:00:24]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/philipj@opera.com/441253003/1

[commit-bot: I haz the power, 2014-08-06 20:00:46]

Change committed as 179647