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

content/renderer/media/mock_media_stream_video_source.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 CONTENT_RENDERER_MEDIA_MOCK_MEDIA_STREAM_VIDEO_SOURCE_H_
 #define CONTENT_RENDERER_MEDIA_MOCK_MEDIA_STREAM_VIDEO_SOURCE_H_
 
 #include "content/renderer/media/media_stream_video_source.h"
 
 #include "testing/gmock/include/gmock/gmock.h"
@@ skipping 26 matching lines @@
   // frame has been delivered.
   void DeliverVideoFrame(const scoped_refptr<media::VideoFrame>& frame);
 
   void CompleteGetSupportedFormats();
 
   const media::VideoCaptureFormat& start_format() const { return format_; }
   int max_requested_height() const { return max_requested_height_; }
   int max_requested_width() const { return max_requested_width_; }
   double max_requested_frame_rate() const { return max_requested_frame_rate_; }
 
-  virtual void SetMutedState(bool muted_state) override {
+  void SetMutedState(bool muted_state) override {
     MediaStreamVideoSource::SetMutedState(muted_state);
     DoSetMutedState(muted_state);
   }
 
  protected:
   // Implements MediaStreamVideoSource.
-  virtual void GetCurrentSupportedFormats(
+  void GetCurrentSupportedFormats(
       int max_requested_height,
       int max_requested_width,
       double max_requested_frame_rate,
       const VideoCaptureDeviceFormatsCB& callback) override;
-  virtual void StartSourceImpl(
+  void StartSourceImpl(
       const media::VideoCaptureFormat& format,
       const VideoCaptureDeliverFrameCB& frame_callback) override;
-  virtual void StopSourceImpl() override;
+  void StopSourceImpl() override;
 
  private:
   media::VideoCaptureFormat format_;
   media::VideoCaptureFormats supported_formats_;
   bool manual_get_supported_formats_;
   int max_requested_height_;
   int max_requested_width_;
   double max_requested_frame_rate_;
   bool attempted_to_start_;
   VideoCaptureDeviceFormatsCB formats_callback_;
   VideoCaptureDeliverFrameCB frame_callback_;
 
   DISALLOW_COPY_AND_ASSIGN(MockMediaStreamVideoSource);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_MEDIA_MOCK_MEDIA_STREAM_VIDEO_SOURCE_H_