old_contents: /**
  * MediaKeys namespace.
  */
  if (typeof MediaKeys == "undefined") var MediaKeys = {};
  
  MediaKeys.basePlayer = "//iframe[@id='main']";
  MediaKeys.playButton = "//button[@id='play' and not(contains(@class,'playing'))]";
  MediaKeys.pauseButton = "//button[@id='play' and contains(@class,'playing')]";
  MediaKeys.skipButton = "//button[@id='next']";
  MediaKeys.previousButton = "//button[@id='previous']"; 
  
new_contents: /**
   * MediaKeys namespace.
   */
  if (typeof MediaKeys == "undefined") var MediaKeys = {};
  
  MediaKeys.basePlayer = "//iframe[@id='main']";
  MediaKeys.playButton = "//button[@id='play' and not(contains(@class,'playing'))]";
  MediaKeys.pauseButton = "//button[@id='play' and contains(@class,'playing')]";
  MediaKeys.skipButton = "//button[@id='next']";
  MediaKeys.previousButton = "//button[@id='previous']";
  
subject: Update player.spotify.com-view.js