Enable navigator.webkitGetUserMedia()

The code came from chrome/browser/media, but was simplified to remove
dependencies on other parts of chrome/ and to always allow the media stream
request.

brightray/browser/browser_client.h

@@ -44,6 +44,7 @@ private:
       int render_process_id,
       int render_view_id,
       int notification_id) OVERRIDE;
+  virtual content::MediaObserver* GetMediaObserver() OVERRIDE;
 
   BrowserMainParts* browser_main_parts_;
   scoped_ptr<NotificationPresenter> notification_presenter_;