anchor.diff:        }
   
       }
  +
  +    void unlisten() {
  +      keydownStream.cancel();
  +      keyupStream.cancel();
  +    }
   }
  
positive.code:     //this.domElement.addEventListener( 'DOMMouseScroll', mousewheel, false ); // firefox
  
      keydownStream = window.onKeyDown.listen(keydown);
      window.onKeyUp.listen(keyup);
  
  
      handleResize();
  
negative.code: 
    StreamSubscription<MouseEvent> mouseMoveStream;
    StreamSubscription<MouseEvent> mouseUpStream;
    StreamSubscription<KeyboardEvent> keydownStream, keyupStream;
  
    EventEmitterEvent changeEvent;
  
  