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

ppapi/proxy/ppp_messaging_proxy.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_PPP_MESSAGING_PROXY_H_
 #define PPAPI_PROXY_PPP_MESSAGING_PROXY_H_
 
 #include "base/compiler_specific.h"
 #include "ppapi/c/pp_instance.h"
 #include "ppapi/c/ppp_messaging.h"
 #include "ppapi/proxy/interface_proxy.h"
 
 namespace ppapi {
 namespace proxy {
 
 class SerializedVarReceiveInput;
 
 class PPP_Messaging_Proxy : public InterfaceProxy {
  public:
   PPP_Messaging_Proxy(Dispatcher* dispatcher);
-  virtual ~PPP_Messaging_Proxy();
+  ~PPP_Messaging_Proxy() override;
 
   // InterfaceProxy implementation.
-  virtual bool OnMessageReceived(const IPC::Message& msg) override;
+  bool OnMessageReceived(const IPC::Message& msg) override;
 
  private:
   // Message handlers.
   void OnMsgHandleMessage(PP_Instance instance,
                           SerializedVarReceiveInput data);
   void OnMsgHandleBlockingMessage(PP_Instance instance,
                                   SerializedVarReceiveInput data,
                                   IPC::Message* reply);
 
   // When this proxy is in the plugin side, this value caches the interface
   // pointer so we don't have to retrieve it from the dispatcher each time.
   // In the host, this value is always NULL.
   const PPP_Messaging* ppp_messaging_impl_;
 
   DISALLOW_COPY_AND_ASSIGN(PPP_Messaging_Proxy);
 };
 
 }  // namespace proxy
 }  // namespace ppapi
 
 #endif  // PPAPI_PROXY_PPP_MESSAGING_PROXY_H_