Hookup the MediaStream glue for Adding and Removing tracks to an existing MediaStream.

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 bd125b50fc1f6158a16dfc1e9178f0ad9cbc5c69..de5f2e180d61fd7c31b3b7c2402ffa965f780700 100644
--- a/content/renderer/media/media_stream_center.h
+++ b/content/renderer/media/media_stream_center.h
@@ -42,6 +42,14 @@ class CONTENT_EXPORT MediaStreamCenter
   virtual void didCreateMediaStream(
       WebKit::WebMediaStream& stream) OVERRIDE;
 
+  virtual bool didAddMediaStreamTrack(
+      const WebKit::WebMediaStream& stream,
+      const WebKit::WebMediaStreamTrack& track) OVERRIDE;
+
+  virtual bool didRemoveMediaStreamTrack(
+      const WebKit::WebMediaStream& stream,
+      const WebKit::WebMediaStreamTrack& track) OVERRIDE;
+
  private:
   // |rtc_factory_| is a weak pointer and is owned by the RenderThreadImpl.
   // It is valid as long as  RenderThreadImpl exist.