cc: Plumb group id through animation creation and start/finish notifications

cc: Plumb group id through animation creation and start/finish notifications

This is required for Blink to track the synchronized starting of groups of
animations.

Blink side plumbing: https://codereview.chromium.org/652593003
Blink usage: https://codereview.chromium.org/651103002

BUG=423265
Committed: https://crrev.com/af2a117bc134fda5a292754e7be5d0072ec6a891
Cr-Commit-Position: refs/heads/master@{#299979}

[dstockwell, 2014-10-16 06:30:09]

dstockwell@chromium.org changed reviewers:
+ ajuma@chromium.org

[ajuma, 2014-10-16 13:25:55]

lgtm

[dstockwell, 2014-10-16 21:18:15]

The CQ bit was checked by dstockwell@chromium.org

[commit-bot: I haz the power, 2014-10-16 21:20:21]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/653563003/220001

[commit-bot: I haz the power, 2014-10-16 21:42:46]

Committed patchset #3 (id:220001)

[commit-bot: I haz the power, 2014-10-16 21:44:11]

Patchset 3 (id:??) landed as
https://crrev.com/af2a117bc134fda5a292754e7be5d0072ec6a891
Cr-Commit-Position: refs/heads/master@{#299979}