cc: Don't schedule top controls animation when there isn't one

cc: Don't schedule top controls animation when there isn't one

If the top controls manager calculates an animation scroll delta of
zero, we schedule another animation attempt for the following frame.
This causes the compositor to run constantly -- for instance -- on pages
where scrolling JavaScript-driven instead of impl-driven.

The fix is to bail out if there is no active top controls animation.

TEST=LayerTreeHostImplWithTopControlsTest.NoIdleAnimation
BUG=309648
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=251770

[Sami, 2014-02-17 17:29:48]

Looks like this bug snuck in through this patch:
https://codereview.chromium.org/131373004

PTAL, thanks!

[aelias_OOO_until_Jul13, 2014-02-17 22:44:44]

On 2014/02/17 17:29:48, Sami wrote:
> Looks like this bug snuck in through this patch:
> https://codereview.chromium.org/131373004
> 
> PTAL, thanks!

lgtm

[Sami, 2014-02-18 11:15:51]

The CQ bit was checked by skyostil@chromium.org

[commit-bot: I haz the power, 2014-02-18 11:16:02]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/skyostil@chromium.org/167013003/40001

[commit-bot: I haz the power, 2014-02-18 12:56:22]

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

[commit-bot: I haz the power, 2014-02-18 12:56:23]

Retried try job too often on win_rel for step(s) unit_tests
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=win_rel&nu...

[Sami, 2014-02-18 12:59:48]

The CQ bit was checked by skyostil@chromium.org

[commit-bot: I haz the power, 2014-02-18 13:00:14]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/skyostil@chromium.org/167013003/40001

[commit-bot: I haz the power, 2014-02-18 16:31:10]

Change committed as 251770