cc: return resources via a ReturnedResource struct rather than TransferableResource

cc/resources/transferable_resource.h

Index: cc/resources/transferable_resource.h
diff --git a/cc/resources/transferable_resource.h b/cc/resources/transferable_resource.h
index 5c979433c90c1f13cba2949b3f963ef76bf87c8c..be6902c313163efe012a92ab80e9195f980210de 100644
--- a/cc/resources/transferable_resource.h
+++ b/cc/resources/transferable_resource.h
@@ -14,10 +14,19 @@
 
 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;
@@ -26,8 +35,6 @@ struct CC_EXPORT TransferableResource {
   gpu::Mailbox mailbox;
 };
 
-typedef std::vector<TransferableResource> TransferableResourceArray;
-
 }  // namespace cc
 
 #endif  // CC_RESOURCES_TRANSFERABLE_RESOURCE_H_