Deflake virtual/threaded/animations/responsive-neutral-keyframes.html

Deflake virtual/threaded/animations/responsive-neutral-keyframes.html

This test was relying on animation events to function. This change
updates the test to use requestAnimationFrame to be more deterministic
and avoid timing out when running under threaded debug.

BUG=469683
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=200772

[alancutter (OOO until 2018), 2015-08-18 08:19:47]

alancutter@chromium.org changed reviewers:
+ timloh@chromium.org

[alancutter (OOO until 2018), 2015-08-18 08:20:05]

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

[commit-bot: I haz the power, 2015-08-18 08:20:18]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1292893005/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1292893005/1

[Timothy Loh, 2015-08-18 08:26:49]

lgtm

[commit-bot: I haz the power, 2015-08-18 09:04:42]

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

[commit-bot: I haz the power, 2015-08-18 09:04:42]

Dry run: This issue passed the CQ dry run.

[alancutter (OOO until 2018), 2015-08-19 00:53:49]

The CQ bit was checked by alancutter@chromium.org

[commit-bot: I haz the power, 2015-08-19 00:54:16]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1292893005/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1292893005/1

[commit-bot: I haz the power, 2015-08-19 00:58:42]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=200772