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

cc/animation/animation_delegate.h

Index: cc/animation/animation_delegate.h
diff --git a/cc/animation/animation_delegate.h b/cc/animation/animation_delegate.h
index d2ab984cac32e5a0e25a9440bdc0c737e896ba76..8c736b5fe6e7466da3d1035a4a7cf41f1fa9718c 100644
--- a/cc/animation/animation_delegate.h
+++ b/cc/animation/animation_delegate.h
@@ -12,12 +12,13 @@ namespace cc {
 
 class CC_EXPORT AnimationDelegate {
  public:
-  virtual void NotifyAnimationStarted(
-      base::TimeTicks monotonic_time,
-      Animation::TargetProperty target_property) = 0;
+  virtual void NotifyAnimationStarted(base::TimeTicks monotonic_time,
+                                      Animation::TargetProperty target_property,
+                                      int group) = 0;
   virtual void NotifyAnimationFinished(
       base::TimeTicks monotonic_time,
-      Animation::TargetProperty target_property) = 0;
+      Animation::TargetProperty target_property,
+      int group) = 0;
 
  protected:
   virtual ~AnimationDelegate() {}