cc: Cleanup class/struct forward declarations

cc/surfaces/display_client.h

 // Copyright 2014 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_SURFACES_DISPLAY_CLIENT_H_
 #define CC_SURFACES_DISPLAY_CLIENT_H_
 
 #include "cc/quads/render_pass.h"
 
 namespace cc {
-struct ManagedMemoryPolicy;
 
 class DisplayClient {
  public:
   virtual ~DisplayClient() {}
   virtual void DisplayOutputSurfaceLost() = 0;
   virtual void DisplayWillDrawAndSwap(bool will_draw_and_swap,
                                       const RenderPassList& render_passes) = 0;
   virtual void DisplayDidDrawAndSwap() = 0;
 };
 
 }  // namespace cc
 
 #endif  // CC_SURFACES_DISPLAY_CLIENT_H_