Surfaces: Receive resources only once

cc/resources/returned_resource.h

 // Copyright 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_RESOURCES_RETURNED_RESOURCE_H_
 #define CC_RESOURCES_RETURNED_RESOURCE_H_
 
 #include <vector>
 
 #include "cc/base/cc_export.h"
 #include "cc/base/resource_id.h"
 #include "gpu/command_buffer/common/sync_token.h"
 
 namespace cc {
 
 // A ReturnedResource is a struct passed along to a child compositor from a
 // parent compositor that corresponds to a TransferableResource that was
 // first passed to the parent compositor.
 struct CC_EXPORT ReturnedResource {
   ReturnedResource() : id(0), count(0), lost(false) {}
+
+  bool operator==(const ReturnedResource& other) const {
+    return id == other.id && sync_token == other.sync_token &&
+           count == other.count && lost == other.lost;
+  }
+
+  bool operator!=(const ReturnedResource& other) const {
+    return !(*this == other);
+  }
+
   // |id| is an identifier generated by the child compositor that uniquely
   // identifies a resource. This is the same ID space as TransferableResource.
   ResourceId id;
 
   // A |sync_token| is an identifier for a point in the parent compositor's
   // command buffer. The child compositor then issues a WaitSyncPointCHROMIUM
   // command with this |sync_token| as a parameter into its own command buffer.
   // This ensures that uses of the resource submitted by the parent compositor
   // are executed before commands submitted by the child.
   gpu::SyncToken sync_token;
 
   // |count| is a reference count for this resource. A resource may be used
   // by mulitple compositor frames submitted to the parent compositor. |count|
   // is the number of references being returned back to the child compositor.
   int count;
 
   // If the resource is lost, then the returner cannot give a sync point for it,
   // and so it has taken ownership of the resource. The receiver cannot do
   // anything with the resource except delete it.
   bool lost;
 };
 
 typedef std::vector<ReturnedResource> ReturnedResourceArray;
 
 }  // namespace cc
 
 #endif  // CC_RESOURCES_RETURNED_RESOURCE_H_