code: protected ListenerSubscription registerElemErrListener(MediaElement element) {
  		return element.addErrorListener(new EventListener<ErrorEvent>() {
  			@Override
  			public void onEvent(ErrorEvent event) {
  				owner.sendMediaError(event);
  			}
  		});
  	}
docs: Registers a listener for when the {@link MediaElement} triggers an
  {@link ErrorEvent}. Notifies the owner with the error.
  
  @param element the {@link MediaElement}
  @return {@link ListenerSubscription} that can be used to deregister the
  listener