anchor.diff:  
     void _startDrag(e) {
       if (stage != null) {
  -      _stopScrolling();
  +      _stopDrag();
         _lastPos.setTo(e.stageX, e.stageY);
         stage.onTouchMove.listen(_stageMoveHandler);
         stage.onTouchEnd.listen(_stageUpHandler);
  
positive.code:     }
    }
  
    void _stopScrolling() {
      _showScrollBars();
      stage.removeEventListener(TouchEvent.TOUCH_MOVE, _stageMoveHandler);
      stage.removeEventListener(TouchEvent.TOUCH_END, _stageUpHandler);
  
negative.code:   ScrollBar _hbar, _vbar;
    Point<num> _viewport;
  
    ScrollView() : super() {
      _hbar = new ScrollBar(orientation: Orientation.HORIZONTAL)..visible = false;
      addChild(_hbar);
      _vbar = new ScrollBar(orientation: Orientation.VERTICAL)..visible = false;
  