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

Review URL: https://chromiumcodereview.appspot.com/11787013

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@175405 0039d316-1c4b-4281-b951-d872f2087c98

tools/perf/page_sets/animations.json → tools/perf/page_sets/tough_animation_cases.json

@@ -2,7 +2,7 @@
   "description": "A collection of animation performance tests",
   "pages": [
     {
-      "url": "file:///animations/keyframed_animations.html",
+      "url": "file:///tough_animation_cases/keyframed_animations.html",
       "why": "Tests various keyframed animations.",
       "smoothness": {
         "action": "wait_interaction",
@@ -10,7 +10,7 @@
       }
     },
     {
-      "url": "file:///animations/transform_transitions.html",
+      "url": "file:///tough_animation_cases/transform_transitions.html",
       "why": "Tests various transitions.",
       "smoothness": {
         "action": "wait_interaction",