Make fast/layers/layer-visibility-sublayer.html unflaky

Make fast/layers/layer-visibility-sublayer.html unflaky

This change makes layer-visibility-sublayer.html into a proper
async test instead of one that relies on setTimeout.

We need to rebaseline because most of the baselines show
the wrong side of the race condition. LOL.

BUG=488185
NOTRY=true

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=196444

[Justin Novosad, 2015-06-03 18:07:23]

junov@chromium.org changed reviewers:
+ enne@chromium.org, esprehn@chromium.org

[Justin Novosad, 2015-06-03 18:07:25]

PTAL

[Justin Novosad, 2015-06-03 18:08:18]

Slow gardening day... got bored...

[esprehn, 2015-06-03 18:13:56]

lgtm! Yay less flake. :)

[Justin Novosad, 2015-06-03 18:14:56]

The CQ bit was checked by junov@chromium.org

[commit-bot: I haz the power, 2015-06-03 18:15:28]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1167833002/1

[commit-bot: I haz the power, 2015-06-03 21:16:56]

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

[commit-bot: I haz the power, 2015-06-03 21:16:56]

Try jobs failed on following builders:
  win_blink_rel on tryserver.blink (JOB_FAILED,
http://build.chromium.org/p/tryserver.blink/builders/win_blink_rel/builds/65092)

[Justin Novosad, 2015-06-04 02:26:48]

The CQ bit was checked by junov@chromium.org

[commit-bot: I haz the power, 2015-06-04 02:27:04]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1167833002/1

[commit-bot: I haz the power, 2015-06-04 02:31:57]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=196444