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

ppapi/proxy/media_stream_track_resource_base.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 PPAPI_PROXY_MEDIA_STREAM_TRACK_RESOURCE_BASE_H_
 #define PPAPI_PROXY_MEDIA_STREAM_TRACK_RESOURCE_BASE_H_
 
 #include "ppapi/proxy/plugin_resource.h"
 #include "ppapi/proxy/ppapi_proxy_export.h"
 #include "ppapi/shared_impl/media_stream_buffer_manager.h"
 
 namespace ppapi {
 namespace proxy {
 
 class PPAPI_PROXY_EXPORT MediaStreamTrackResourceBase
   : public PluginResource,
     public MediaStreamBufferManager::Delegate {
  protected:
   MediaStreamTrackResourceBase(Connection connection,
                                PP_Instance instance,
                                int pending_renderer_id,
                                const std::string& id);
 
   MediaStreamTrackResourceBase(Connection connection, PP_Instance instance);
 
-  virtual ~MediaStreamTrackResourceBase();
+  ~MediaStreamTrackResourceBase() override;
 
   std::string id() const { return id_; }
 
   void set_id(const std::string& id) { id_ = id; }
 
   bool has_ended() const { return has_ended_; }
 
   MediaStreamBufferManager* buffer_manager() { return &buffer_manager_; }
 
   void CloseInternal();
 
   // Sends a buffer index to the corresponding PepperMediaStreamTrackHostBase
   // via an IPC message. The host adds the buffer index into its
   // |buffer_manager_| for reading or writing.
   // Also see |MediaStreamBufferManager|.
   void SendEnqueueBufferMessageToHost(int32_t index);
 
   // PluginResource overrides:
-  virtual void OnReplyReceived(const ResourceMessageReplyParams& params,
-                               const IPC::Message& msg) override;
+  void OnReplyReceived(const ResourceMessageReplyParams& params,
+                       const IPC::Message& msg) override;
 
  private:
   // Message handlers:
   void OnPluginMsgInitBuffers(const ResourceMessageReplyParams& params,
                               int32_t number_of_buffers,
                               int32_t buffer_size,
                               bool readonly);
   void OnPluginMsgEnqueueBuffer(const ResourceMessageReplyParams& params,
                                 int32_t index);
   void OnPluginMsgEnqueueBuffers(const ResourceMessageReplyParams& params,
                                  const std::vector<int32_t>& indices);
 
   MediaStreamBufferManager buffer_manager_;
 
   std::string id_;
 
   bool has_ended_;
 
   DISALLOW_COPY_AND_ASSIGN(MediaStreamTrackResourceBase);
 };
 
 }  // namespace proxy
 }  // namespace ppapi
 
 #endif  // PPAPI_PROXY_MEDIA_STREAM_TRACK_RESOURCE_BASE_H_