CC Animations: Make LayerAnimationController creation optional

cc/layers/layer.h

Index: cc/layers/layer.h
diff --git a/cc/layers/layer.h b/cc/layers/layer.h
index 6f10725b08ff536bc30d8b4c5bb05a8198b85856..3a6eb4d12e884f23b32996ac0a91998237289f43 100644
--- a/cc/layers/layer.h
+++ b/cc/layers/layer.h
@@ -61,6 +61,7 @@ class LayerImpl;
 class LayerTreeHost;
 class LayerTreeHostCommon;
 class LayerTreeImpl;
+class LayerTreeSettings;
 class PriorityCalculator;
 class RenderingStatsInstrumentation;
 class ResourceUpdateQueue;
@@ -412,6 +413,8 @@ class CC_EXPORT Layer : public base::RefCounted<Layer>,
   // Set the priority of all desired textures in this layer.
   virtual void SetTexturePriorities(const PriorityCalculator& priority_calc) {}
 
+  static void SetCompositorAnimationTimelinesEnabled(bool enabled);
+
   bool AddAnimation(scoped_ptr<Animation> animation);
   void PauseAnimation(int animation_id, double time_offset);
   void RemoveAnimation(int animation_id);
@@ -424,10 +427,13 @@ class CC_EXPORT Layer : public base::RefCounted<Layer>,
       scoped_refptr<LayerAnimationController> controller);
 
   void set_layer_animation_delegate(AnimationDelegate* delegate) {
+    DCHECK(layer_animation_controller_);

[danakj, 2015/05/08 18:21:40]

i don't think this DCHECK is doing much for you? you'd just null-deref on the
next line anyways.

[loyso (OOO), 2015/05/11 06:59:43]

It makes the problem clear. null-deref is undefined behavior.

     layer_animation_controller_->set_layer_animation_delegate(delegate);
   }
 
   bool HasActiveAnimation() const;
+  void RegisterForAnimations(AnimationRegistrar* registrar,
+                             const LayerTreeSettings& settings);
 
   void AddLayerAnimationEventObserver(
       LayerAnimationEventObserver* animation_observer);