AnimationTimeline::serviceAnimations should reserveInitialCapacity

AnimationTimeline::serviceAnimations should reserveInitialCapacity

Rather than reallocating the players vector, we can just reserve exactly the
correct capacity ahead of time. I didn't see these mallocs on a profile, but
this code is executed every frame during composited animations.

R=dstockwell@chromium.org

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=177053

[dstockwell, 2014-06-26 23:13:47]

lgtm

[commit-bot: I haz the power, 2014-06-26 23:14:59]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/abarth@chromium.org/353083002/1

[commit-bot: I haz the power, 2014-06-27 02:31:06]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  linux_chromium_gn_rel on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/linux_chromium_gn_rel/bu...)
  win_blink_rel on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/win_blink_rel/builds/13903)

[commit-bot: I haz the power, 2014-06-27 02:37:02]

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

[commit-bot: I haz the power, 2014-06-27 02:37:03]

Try jobs failed on following builders:
  linux_chromium_gn_rel on tryserver.blink
(http://build.chromium.org/p/tryserver.blink/builders/linux_chromium_gn_rel/bu...)

[abarth-chromium, 2014-06-27 03:14:10]

The CQ bit was checked by abarth@chromium.org

[commit-bot: I haz the power, 2014-06-27 03:15:35]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/abarth@chromium.org/353083002/1

[commit-bot: I haz the power, 2014-06-27 03:33:32]

Change committed as 177053