Do not give GPU memory to backgrounded compositors.

cc/output/context_provider.h

 // Copyright (c) 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_OUTPUT_CONTEXT_PROVIDER_H_
 #define CC_OUTPUT_CONTEXT_PROVIDER_H_
 
 #include "base/callback.h"
 #include "base/memory/ref_counted.h"
 #include "cc/base/cc_export.h"
@@ skipping 60 matching lines @@
       const LostContextCallback& lost_context_callback) = 0;
 
   // Sets a callback to be called when swap buffers completes. This should be
   // called from the same thread that the context is bound to.
   typedef base::Closure SwapBuffersCompleteCallback;
   virtual void SetSwapBuffersCompleteCallback(
       const SwapBuffersCompleteCallback& swap_buffers_complete_callback) = 0;
 
   // Sets a callback to be called when the memory policy changes. This should be
   // called from the same thread that the context is bound to.
-  typedef base::Callback<void(
-    const cc::ManagedMemoryPolicy& policy,
-    bool discard_backbuffer_when_not_visible)> MemoryPolicyChangedCallback;
+  typedef base::Callback<void(const cc::ManagedMemoryPolicy& policy)>
+      MemoryPolicyChangedCallback;
   virtual void SetMemoryPolicyChangedCallback(
       const MemoryPolicyChangedCallback& memory_policy_changed_callback) = 0;
 
  protected:
   friend class base::RefCountedThreadSafe<ContextProvider>;
   virtual ~ContextProvider() {}
 };
 
 }  // namespace cc
 
 #endif  // CC_OUTPUT_CONTEXT_PROVIDER_H_