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

cc/layers/layer_impl.h

Index: cc/layers/layer_impl.h
diff --git a/cc/layers/layer_impl.h b/cc/layers/layer_impl.h
index b7f382227fe58b48f0e957a5d6ed45012077c29f..45e80d378fadc14505705b2b788751655aae5021 100644
--- a/cc/layers/layer_impl.h
+++ b/cc/layers/layer_impl.h
@@ -110,12 +110,13 @@ class CC_EXPORT LayerImpl : public LayerAnimationValueObserver,
   virtual bool IsActive() const override;
 
   // AnimationDelegate implementation.
-  virtual void NotifyAnimationStarted(
-      base::TimeTicks monotonic_time,
-      Animation::TargetProperty target_property) override{};
+  virtual void NotifyAnimationStarted(base::TimeTicks monotonic_time,
+                                      Animation::TargetProperty target_property,
+                                      int group) override{};
   virtual void NotifyAnimationFinished(
       base::TimeTicks monotonic_time,
-      Animation::TargetProperty target_property) override;
+      Animation::TargetProperty target_property,
+      int group) override;
 
   // Tree structure.
   LayerImpl* parent() { return parent_; }