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