Do not give GPU memory to backgrounded compositors.

cc/output/output_surface.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_OUTPUT_OUTPUT_SURFACE_H_
 #define CC_OUTPUT_OUTPUT_SURFACE_H_
 
 #include <deque>
 
 #include "base/basictypes.h"
@@ skipping 181 matching lines @@
   // virtual for testing.
   virtual base::TimeTicks RetroactiveBeginImplFrameDeadline();
   virtual void PostCheckForRetroactiveBeginImplFrame();
   void CheckForRetroactiveBeginImplFrame();
 
  private:
   OutputSurfaceClient* client_;
 
   void SetUpContext3d();
   void ResetContext3d();
-  void SetMemoryPolicy(const ManagedMemoryPolicy& policy,
-                       bool discard_backbuffer_when_not_visible);
+  void SetMemoryPolicy(const ManagedMemoryPolicy& policy);
   void UpdateAndMeasureGpuLatency();
 
   // check_for_retroactive_begin_impl_frame_pending_ is used to avoid posting
   // redundant checks for a retroactive BeginImplFrame.
   bool check_for_retroactive_begin_impl_frame_pending_;
 
   bool external_stencil_test_enabled_;
 
   base::WeakPtrFactory<OutputSurface> weak_ptr_factory_;
 
   std::deque<unsigned> available_gpu_latency_query_ids_;
   std::deque<unsigned> pending_gpu_latency_query_ids_;
   RollingTimeDeltaHistory gpu_latency_history_;
 
   DISALLOW_COPY_AND_ASSIGN(OutputSurface);
 };
 
 }  // namespace cc
 
 #endif  // CC_OUTPUT_OUTPUT_SURFACE_H_