Add Web Animations perf tests to tough_animation_cases page set

Add Web Animations perf tests to tough_animation_cases page set

This patch adds the following perf targets to tough_animation_cases:
web_animations_many_keyframes.html?N=0032
web_animations_many_keyframes.html?N=0100
web_animations_many_keyframes.html?N=0316
web_animations_many_keyframes.html?N=1000
web_animations_simultaneous.html?N=0032
web_animations_simultaneous.html?N=0100
web_animations_simultaneous.html?N=0316
web_animations_simultaneous.html?N=1000
web_animations_staggered_chaining.html?N=0032
web_animations_staggered_chaining.html?N=0100
web_animations_staggered_chaining.html?N=0316
web_animations_staggered_chaining.html?N=1000
web_animations_staggered_infinite_iterations.html?N=0032
web_animations_staggered_infinite_iterations.html?N=0100
web_animations_staggered_infinite_iterations.html?N=0316
web_animations_staggered_infinite_iterations.html?N=1000
web_animations_staggered_triggering.html?N=0032
web_animations_staggered_triggering.html?N=0100
web_animations_staggered_triggering.html?N=0316
web_animations_staggered_triggering.html?N=1000

NOTRY=TRUE
BUG=309981
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=281123

[alancutter (OOO until 2018), 2014-07-01 10:28:51]

The FPS readings for these tests on a Nexus 7 device look like:
http://i.imgur.com/opZMNQD.png

[alancutter (OOO until 2018), 2014-07-02 15:24:10]

tonyg: Poke.

[dtu, 2014-07-02 20:11:08]

lgtm

[alancutter (OOO until 2018), 2014-07-03 00:07:24]

The CQ bit was checked by alancutter@chromium.org

[commit-bot: I haz the power, 2014-07-03 00:08:58]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/alancutter@chromium.org/365613002/40001

[commit-bot: I haz the power, 2014-07-03 00:11:32]

Change committed as 281123