CC Animations: Make LayerAnimationController creation optional

ui/compositor/compositor.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef UI_COMPOSITOR_COMPOSITOR_H_
 #define UI_COMPOSITOR_COMPOSITOR_H_
 
 #include <list>
 #include <string>
 
@@ skipping 281 matching lines @@
 
   // cc::LayerTreeHostSingleThreadClient implementation.
   void DidPostSwapBuffers() override;
   void DidAbortSwapBuffers() override;
 
   bool IsLocked() { return compositor_lock_ != NULL; }
 
   const cc::LayerTreeDebugState& GetLayerTreeDebugState() const;
   void SetLayerTreeDebugState(const cc::LayerTreeDebugState& debug_state);
   const cc::RendererSettings& GetRendererSettings() const;
+  const cc::LayerTreeHost& GetLayerTreeHost() const;
 
   LayerAnimatorCollection* layer_animator_collection() {
     return &layer_animator_collection_;
   }
 
   cc::SurfaceIdAllocator* surface_id_allocator() {
     return surface_id_allocator_.get();
   }
 
  private:
@@ skipping 42 matching lines @@
   cc::BeginFrameArgs missed_begin_frame_args_;
 
   base::WeakPtrFactory<Compositor> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(Compositor);
 };
 
 }  // namespace ui
 
 #endif  // UI_COMPOSITOR_COMPOSITOR_H_