Simplify rate limiting since it's main thread shared context only

cc/trees/layer_tree_host_client.h

 // Copyright 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 CC_TREES_LAYER_TREE_HOST_CLIENT_H_
 #define CC_TREES_LAYER_TREE_HOST_CLIENT_H_
 
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 
@@ skipping 26 matching lines @@
   virtual void DidCompleteSwapBuffers() = 0;
 
   // Used only in the single-threaded path.
   virtual void ScheduleComposite() = 0;
 
   // If the client provides an OutputSurface bound to a 3d context for direct
   // rendering, this must return a provider that provides contexts usable from
   // the same thread as the OutputSurface's context.
   virtual scoped_refptr<cc::ContextProvider> OffscreenContextProvider() = 0;
 
+  // Requests that the client insert a rate limiting token in the shared main
+  // thread context's command stream that will block if the context gets too far
+  // ahead of the compositor's command stream. Only needed if the tree contains
+  // a TextureLayer that calls SetRateLimitContext(true).
+  virtual void RateLimitSharedMainThreadContext() {}
+
   // This hook is for testing.
   virtual void DidFailToInitializeOutputSurface() {}
 
  protected:
   virtual ~LayerTreeHostClient() {}
 };
 
 }  // namespace cc
 
 #endif  // CC_TREES_LAYER_TREE_HOST_CLIENT_H_