anchor.diff:      _loadPixels(j['pixels']);
   
       if (!updateZippedJson)
  -      new Timer(new Duration(milliseconds: 800), () => _clearZippedJsonUpdater());
  +      // canncel zippedJson update because the browser history go forward
  +      new Timer(new Duration(milliseconds: 1000), () => _clearZippedJsonUpdater());
     }
   
     void _loadPixels(List<List<int>> pixels) {
  
positive.code:   @override
    attached() {
      super.attached();
      _initController();
      _asyncUpdateContainterSize();
  
      _startUrlFragmentObsevation();
  
      async((_) { _updateZipped();});
      _initLocalStorageProps();
    }
  
negative.code:   @observable bool isStackingHistory = false;
  
    Timer zippedJsonUpdater;
    Function afterRendered;
  
    PixelCanvasElement get canvas => shadowRoot.querySelector('pixel-canvas');
    AnsiColorPaletteElement get _palette =>
  