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

content/renderer/media/media_stream_center.h

Index: content/renderer/media/media_stream_center.h
diff --git a/content/renderer/media/media_stream_center.h b/content/renderer/media/media_stream_center.h
index ef4fbaa0db559ed3c94ab1b1107b6f16d796b6bc..d36275570225298203b5811e086b707789f68653 100644
--- a/content/renderer/media/media_stream_center.h
+++ b/content/renderer/media/media_stream_center.h
@@ -30,37 +30,32 @@ class CONTENT_EXPORT MediaStreamCenter
  public:
   MediaStreamCenter(blink::WebMediaStreamCenterClient* client,
                     PeerConnectionDependencyFactory* factory);
-  virtual ~MediaStreamCenter();
+  ~MediaStreamCenter() override;
 
  private:
-  virtual void didCreateMediaStreamTrack(
+  void didCreateMediaStreamTrack(
       const blink::WebMediaStreamTrack& track) override;
 
-  virtual void didEnableMediaStreamTrack(
+  void didEnableMediaStreamTrack(
       const blink::WebMediaStreamTrack& track) override;
 
-  virtual void didDisableMediaStreamTrack(
+  void didDisableMediaStreamTrack(
       const blink::WebMediaStreamTrack& track) override;
 
-  virtual void didStopLocalMediaStream(
-      const blink::WebMediaStream& stream) override;
+  void didStopLocalMediaStream(const blink::WebMediaStream& stream) override;
 
-  virtual bool didStopMediaStreamTrack(
+  bool didStopMediaStreamTrack(
       const blink::WebMediaStreamTrack& track) override;
 
-  virtual blink::WebAudioSourceProvider*
-      createWebAudioSourceFromMediaStreamTrack(
-          const blink::WebMediaStreamTrack& track) override;
-
+  blink::WebAudioSourceProvider* createWebAudioSourceFromMediaStreamTrack(
+      const blink::WebMediaStreamTrack& track) override;
 
-  virtual void didCreateMediaStream(
-      blink::WebMediaStream& stream) override;
+  void didCreateMediaStream(blink::WebMediaStream& stream) override;
 
-  virtual bool didAddMediaStreamTrack(
-      const blink::WebMediaStream& stream,
-      const blink::WebMediaStreamTrack& track) override;
+  bool didAddMediaStreamTrack(const blink::WebMediaStream& stream,
+                              const blink::WebMediaStreamTrack& track) override;
 
-  virtual bool didRemoveMediaStreamTrack(
+  bool didRemoveMediaStreamTrack(
       const blink::WebMediaStream& stream,
       const blink::WebMediaStreamTrack& track) override;