anchor.diff:  
     PElement(this._width, this._height, [this.cacheEnabled = false]) :
       _transforms = new List<core.AffineTransform>(),
  -    _updatedEventHandle = new core.EventHandle<core.EventArgs>()
  -  {
  -    if(cacheEnabled){
  -      throw 'should probably implement this';
  -    }
  -  }
  +    _updatedEventHandle = new core.EventHandle<core.EventArgs>();
   
     num get width() => _width;
   
  
positive.code:   //
  
    void drawInternal(CanvasRenderingContext2D ctx){
      // until we ar rocking caching, just draw normal
      _drawNormal(ctx);
    }
  
    void _drawNormal(CanvasRenderingContext2D ctx){
  
negative.code:   final List<core.AffineTransform> _transforms;
    final bool cacheEnabled;
    final core.EventHandle<core.EventArgs> _updatedEventHandle;
    CanvasElement _cacheCanvas;
  
    num _width, _height, _alpha;
    core.Size _lastDrawSize;
  