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

ppapi/proxy/video_destination_resource.h

 // Copyright (c) 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 PPAPI_PROXY_VIDEO_DESTINATION_RESOURCE_H_
 #define PPAPI_PROXY_VIDEO_DESTINATION_RESOURCE_H_
 
 #include <string>
 
 #include "ppapi/c/pp_var.h"
 #include "ppapi/proxy/connection.h"
 #include "ppapi/proxy/plugin_resource.h"
 #include "ppapi/proxy/ppapi_proxy_export.h"
 #include "ppapi/thunk/ppb_video_destination_private_api.h"
 
 struct PP_VideoFrame_Private;
 
 namespace ppapi {
 
 class TrackedCallback;
 
 namespace proxy {
 
 class PPAPI_PROXY_EXPORT VideoDestinationResource
     : public PluginResource,
       public thunk::PPB_VideoDestination_Private_API {
  public:
   VideoDestinationResource(Connection connection,
                            PP_Instance instance);
-  virtual ~VideoDestinationResource();
+  ~VideoDestinationResource() override;
 
   // Resource overrides.
-  virtual thunk::PPB_VideoDestination_Private_API*
-      AsPPB_VideoDestination_Private_API() override;
+  thunk::PPB_VideoDestination_Private_API* AsPPB_VideoDestination_Private_API()
+      override;
 
   // PPB_VideoDestination_Private_API implementation.
-  virtual int32_t Open(
+  int32_t Open(
       const PP_Var& stream_url,
       scoped_refptr<TrackedCallback> callback) override;
-  virtual int32_t PutFrame(const PP_VideoFrame_Private& frame) override;
-  virtual void Close() override;
+  int32_t PutFrame(const PP_VideoFrame_Private& frame) override;
+  void Close() override;
 
  private:
   void OnPluginMsgOpenComplete(
       const ResourceMessageReplyParams& params);
 
   scoped_refptr<TrackedCallback> open_callback_;
   bool is_open_;
 
   DISALLOW_COPY_AND_ASSIGN(VideoDestinationResource);
 };
 
 }  // namespace proxy
 }  // namespace ppapi
 
 #endif  // PPAPI_PROXY_VIDEO_DESTINATION_RESOURCE_H_