Make SingleThreadProxy a SchedulerClient

cc/trees/layer_tree_host_single_thread_client.h

 // Copyright 2013 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 CC_TREES_LAYER_TREE_HOST_SINGLE_THREAD_CLIENT_H_
 #define CC_TREES_LAYER_TREE_HOST_SINGLE_THREAD_CLIENT_H_
 
 namespace cc {
 
 class LayerTreeHostSingleThreadClient {
  public:
   // Request that the client schedule a composite.
-  virtual void ScheduleComposite() = 0;
+  virtual void ScheduleComposite() {}
   // Request that the client schedule a composite now, and calculate appropriate
   // delay for potential future frame.
-  virtual void ScheduleAnimation() = 0;
+  virtual void ScheduleAnimation() {}
 
   // Called whenever the compositor posts a SwapBuffers (either full or
   // partial). After DidPostSwapBuffers(), exactly one of
   // DidCompleteSwapBuffers() or DidAbortSwapBuffers() will be called, thus
   // these functions can be used to keep track of pending swap buffers calls for
   // rate limiting.
   virtual void DidPostSwapBuffers() = 0;
   virtual void DidCompleteSwapBuffers() = 0;
   virtual void DidAbortSwapBuffers() = 0;
 
  protected:
   virtual ~LayerTreeHostSingleThreadClient() {}
 };
 
 }  // namespace cc
 
 #endif  // CC_TREES_LAYER_TREE_HOST_SINGLE_THREAD_CLIENT_H_