cc: Support animating scroll offset

cc/animation/layer_animation_controller.h

Index: cc/animation/layer_animation_controller.h
diff --git a/cc/animation/layer_animation_controller.h b/cc/animation/layer_animation_controller.h
index 705fd7f059bc0b756d4ccf35c82a0ba49253dd8a..564a5933e7f70fb400c200f8aba812c42f5f3604 100644
--- a/cc/animation/layer_animation_controller.h
+++ b/cc/animation/layer_animation_controller.h
@@ -30,6 +30,7 @@ class AnimationRegistrar;
 class FilterOperations;
 class KeyframeValueList;
 class LayerAnimationValueObserver;
+class LayerAnimationValueProvider;
 
 class CC_EXPORT LayerAnimationController
     : public base::RefCounted<LayerAnimationController> {
@@ -95,6 +96,15 @@ class CC_EXPORT LayerAnimationController
   void AddEventObserver(LayerAnimationEventObserver* observer);
   void RemoveEventObserver(LayerAnimationEventObserver* observer);
 
+  void set_value_provider(LayerAnimationValueProvider* provider) {
+    value_provider_ = provider;
+  }
+
+  void remove_value_provider(LayerAnimationValueProvider* provider) {
+    if (value_provider_ == provider)
+      value_provider_ = NULL;
+  }
+
   void set_layer_animation_delegate(AnimationDelegate* delegate) {
     layer_animation_delegate_ = delegate;
   }
@@ -136,6 +146,7 @@ class CC_EXPORT LayerAnimationController
   void NotifyObserversOpacityAnimated(float opacity);
   void NotifyObserversTransformAnimated(const gfx::Transform& transform);
   void NotifyObserversFilterAnimated(const FilterOperations& filter);
+  void NotifyObserversScrollOffsetAnimated(gfx::Vector2dF scroll_offset);
 
   void NotifyObserversAnimationWaitingForDeletion();
 
@@ -154,6 +165,8 @@ class CC_EXPORT LayerAnimationController
   ObserverList<LayerAnimationValueObserver> value_observers_;
   ObserverList<LayerAnimationEventObserver> event_observers_;
 
+  LayerAnimationValueProvider* value_provider_;
+
   AnimationDelegate* layer_animation_delegate_;
 
   DISALLOW_COPY_AND_ASSIGN(LayerAnimationController);