anchor.diff:  List<_PaintRequest> _paintQueue = <_PaintRequest>[];
   
   void _recycleCanvas(EngineCanvas? canvas) {
  +  assert(canvas == null || !_recycledCanvases.contains(canvas));
     if (canvas is BitmapCanvas) {
       canvas.setElementCache(null);
       if (canvas.isReusable()) {
  
positive.code:   @override
    void discard() {
      _recycleCanvas(_canvas);
      super.discard();
    }
  
  
negative.code:       if (rootElement != null) {
          domRenderer.clearDom(rootElement!);
        }
        if (_canvas != null && _canvas != oldCanvas) {
          _recycleCanvas(_canvas);
        }
        _canvas = null;
  