cc: return resources via a ReturnedResource struct rather than TransferableResource

cc/resources/transferable_resource.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_RESOURCES_TRANSFERABLE_RESOURCE_H_
 #define CC_RESOURCES_TRANSFERABLE_RESOURCE_H_
 
 #include <vector>
 
 #include "base/basictypes.h"
 #include "cc/base/cc_export.h"
 #include "gpu/command_buffer/common/mailbox.h"
 #include "ui/gfx/size.h"
 
 namespace cc {
 
+struct ReturnedResource;
+typedef std::vector<ReturnedResource> ReturnedResourceArray;
+struct TransferableResource;
+typedef std::vector<TransferableResource> TransferableResourceArray;
+
 struct CC_EXPORT TransferableResource {
   TransferableResource();
   ~TransferableResource();
 
+  ReturnedResource ToReturnedResource() const;
+  static void ReturnResources(const TransferableResourceArray& input,
+                              ReturnedResourceArray* output);
+
   unsigned id;
   unsigned sync_point;
   uint32 format;
   uint32 filter;
   gfx::Size size;
   gpu::Mailbox mailbox;
 };
 
-typedef std::vector<TransferableResource> TransferableResourceArray;
-
 }  // namespace cc
 
 #endif  // CC_RESOURCES_TRANSFERABLE_RESOURCE_H_