Rename animations pageset to tough_animation_cases

Rename animations pageset to tough_animation_cases

We're using tough_blah_cases terminology for other content-specific
collections. So lets do that here as well.

R=hartmanng
CC=vollick
NOTRY=True

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=175405

[nduca, 2013-01-05 06:43:12]

ian, glenn, wdyt?

[hartmanng, 2013-01-06 19:15:58]

Makes sense, LGTM

[commit-bot: I haz the power, 2013-01-07 17:51:01]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/nduca@chromium.org/11787013/1

[commit-bot: I haz the power, 2013-01-07 19:57:19]

Retried try job too often on win_aura for step(s) interactive_ui_tests

[commit-bot: I haz the power, 2013-01-07 22:34:26]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/nduca@chromium.org/11787013/1

[commit-bot: I haz the power, 2013-01-07 22:39:12]

Change committed as 175405