anchor.diff:      }
   
       var oldRendered = _rendered;
  +    bool mounting = oldRendered == null;
       int lastOrder = _currentOrder;
       _currentOrder = _order;
       _currentlyRendering = this;
  
positive.code:     }
      _root = _rendered._root;
      assert(_rendered._root is sky.Node);
    }
  
    void _renderIfDirty() {
  
negative.code:         _order = _currentOrder + 1,
          super(key:key);
  
    void didMount() {}
    void didUnmount() {}
  
    void _remove() {
  