anchor.diff:      Object key,
       List<UINode> children,
       this.direction: FlexDirection.Horizontal
  -  }) : super(
  -    key: key,
  -    children: children
  -  );
  +  }) : super(key: key, children: children);
   
     void syncRenderNode(UINode old) {
       super.syncRenderNode(old);
  
positive.code: }
  
  class Rectangle extends RenderNodeWrapper {
  
    Rectangle(this.color, {
      Object key
    }) : super(
      key: key
    );
  
    final int color;
  
    RenderSolidColor root;
    RenderSolidColor createNode() => new RenderSolidColor(color, desiredSize: new sky.Size(40.0, 130.0));
  
    static final Rectangle _emptyRectangle = new Rectangle(0);
    RenderNodeWrapper get emptyNode => _emptyRectangle;
  
  }
  
negative.code:       var ancestor = findAncestor(RenderNodeWrapper);
        if (ancestor is RenderNodeWrapper)
          ancestor.insert(this, slot);
      } else {
        root = old.root;
        assert(root != null);
  