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

ppapi/proxy/ppb_x509_certificate_private_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_PPB_X509_CERTIFICATE_PRIVATE_PROXY_H_
 #define PPAPI_PROXY_PPB_X509_CERTIFICATE_PRIVATE_PROXY_H_
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "ppapi/c/pp_instance.h"
 #include "ppapi/c/pp_resource.h"
 #include "ppapi/proxy/interface_proxy.h"
 
 namespace ppapi {
 namespace proxy {
 
 class PPB_X509Certificate_Private_Proxy
     : public InterfaceProxy {
  public:
   explicit PPB_X509Certificate_Private_Proxy(Dispatcher* dispatcher);
-  virtual ~PPB_X509Certificate_Private_Proxy();
+  ~PPB_X509Certificate_Private_Proxy() override;
   static PP_Resource CreateProxyResource(PP_Instance instance);
 
   // InterfaceProxy implementation.
-  virtual bool OnMessageReceived(const IPC::Message& msg) override;
+  bool OnMessageReceived(const IPC::Message& msg) override;
 
   static const ApiID kApiID = API_ID_PPB_X509_CERTIFICATE_PRIVATE;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(PPB_X509Certificate_Private_Proxy);
 };
 
 }  // namespace proxy
 }  // namespace ppapi
 
 #endif  // PPAPI_PROXY_PPB_X509_CERTIFICATE_PRIVATE_PROXY_H_