Fix memory leak in Sync FakeServerEntity

sync/test/fake_server/tombstone_entity.h

 // Copyright 2014 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 SYNC_TEST_FAKE_SERVER_TOMBSTONE_ENTITY_H_
 #define SYNC_TEST_FAKE_SERVER_TOMBSTONE_ENTITY_H_
 
 #include <string>
 
 #include "base/basictypes.h"
 #include "sync/internal_api/public/base/model_type.h"
 #include "sync/protocol/sync.pb.h"
 #include "sync/test/fake_server/fake_server_entity.h"
 
 namespace fake_server {
 
 // A Sync entity that represents a deleted item.
 class TombstoneEntity : public FakeServerEntity {
  public:
   virtual ~TombstoneEntity();
 
   // Factory function for TombstoneEntity.
   static FakeServerEntity* Create(const std::string& id);
 
   // FakeServerEntity implementation.
   virtual std::string GetParentId() const OVERRIDE;
-  virtual sync_pb::SyncEntity* SerializeAsProto() OVERRIDE;
+  virtual void SerializeAsProto(sync_pb::SyncEntity* proto) OVERRIDE;
   virtual bool IsDeleted() const OVERRIDE;
   virtual bool IsFolder() const OVERRIDE;
 
  private:
   TombstoneEntity(const std::string& id, const syncer::ModelType& model_type);
 };
 
 }  // namespace fake_server
 
 #endif  // SYNC_TEST_FAKE_SERVER_TOMBSTONE_ENTITY_H_