Add Web Animations performance tests

Add Web Animations performance tests

This adds several performance tests for Web Animations initiated in
various ways.

BUG=421733
Committed: https://crrev.com/8a73dce8691fa957b5bbbfbd6221c1c77ef1c1cd
Cr-Commit-Position: refs/heads/master@{#301567}

[alancutter (OOO until 2018), 2014-10-21 03:46:27]

alancutter@chromium.org changed reviewers:
+ dtu@chromium.org, tonyg@chromium.org

[alancutter (OOO until 2018), 2014-10-21 03:46:28]

This change builds upon the Add CSS Animations performance tests CL:
https://codereview.chromium.org/665833002/

Nexus 5 trybot run status: https://codereview.chromium.org/664323002/

[tonyg, 2014-10-21 23:36:05]

lgtm

[alancutter (OOO until 2018), 2014-10-28 04:29:06]

The CQ bit was checked by alancutter@chromium.org

[commit-bot: I haz the power, 2014-10-28 04:30:21]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/665893005/20001

[commit-bot: I haz the power, 2014-10-28 05:31:48]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2014-10-28 05:32:32]

Patchset 2 (id:??) landed as
https://crrev.com/8a73dce8691fa957b5bbbfbd6221c1c77ef1c1cd
Cr-Commit-Position: refs/heads/master@{#301567}