CC Animations: Make LayerAnimationController creation optional

ui/compositor/layer.h

Index: ui/compositor/layer.h
diff --git a/ui/compositor/layer.h b/ui/compositor/layer.h
index bb8b1af6de89c7dd944136a3df2c4b080d88b62b..17cfb7500e78cb6239e65a569dd991a20b5b3d74 100644
--- a/ui/compositor/layer.h
+++ b/ui/compositor/layer.h
@@ -89,6 +89,8 @@ class COMPOSITOR_EXPORT Layer
   // Called by the compositor when the Layer is set as its root Layer. This can
   // only ever be called on the root layer.
   void SetCompositor(Compositor* compositor);
+  void SetCompositorRootCCLayer(scoped_refptr<cc::Layer> root_layer);
+  void ResetCompositor();
 
   LayerDelegate* delegate() { return delegate_; }
   void set_delegate(LayerDelegate* delegate) { delegate_ = delegate; }
@@ -141,6 +143,8 @@ class COMPOSITOR_EXPORT Layer
   void SetTransform(const gfx::Transform& transform);
   gfx::Transform transform() const;
 
+  gfx::PointF position() const { return cc_layer_->position(); }
+
   // Return the target transform if animator is running, or the current
   // transform otherwise.
   gfx::Transform GetTargetTransform() const;
@@ -350,7 +354,7 @@ class COMPOSITOR_EXPORT Layer
       ContentLayerClient::PaintingControlSetting painting_control) override;
   bool FillsBoundsCompletely() const override;
 
-  cc::Layer* cc_layer() { return cc_layer_; }
+  cc::Layer* cc_layer_for_testing() { return cc_layer_; }
 
   // TextureLayerClient
   bool PrepareTextureMailbox(
@@ -416,6 +420,10 @@ class COMPOSITOR_EXPORT Layer
   // Creates a corresponding composited layer for |type_|.
   void CreateCcLayer();
 
+  // Attach/Detach CC Layer animation event observers.
+  void AttachAnimationObservers();
+  void DetachAnimationObservers();
+
   // Recomputes and sets to |cc_layer_|.
   void RecomputeDrawsContentAndUVRect();
   void RecomputePosition();