Update {virtual,override} to follow C++11 style in ppapi.

ppapi/proxy/broker_resource.h

 // Copyright (c) 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 PPAPI_PROXY_BROKER_RESOURCE_H_
 #define PPAPI_PROXY_BROKER_RESOURCE_H_
 
 #include "ppapi/proxy/connection.h"
 #include "ppapi/proxy/plugin_resource.h"
 #include "ppapi/thunk/ppb_broker_api.h"
 
 namespace ppapi {
 namespace proxy {
 
 class BrokerResource
     : public PluginResource,
       public thunk::PPB_Broker_Instance_API {
  public:
   BrokerResource(Connection connection, PP_Instance instance);
-  virtual ~BrokerResource();
+  ~BrokerResource() override;
 
   // Resource override.
-  virtual thunk::PPB_Broker_Instance_API* AsPPB_Broker_Instance_API() override;
+  thunk::PPB_Broker_Instance_API* AsPPB_Broker_Instance_API() override;
 
   // thunk::PPB_Broker_Instance_API implementation.
-  virtual PP_Bool IsAllowed() override;
+  PP_Bool IsAllowed() override;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(BrokerResource);
 };
 
 }  // namespace proxy
 }  // namespace ppapi
 
 #endif  // PPAPI_PROXY_BROKER_RESOURCE_H_