anchor.diff:      _trace('_sync($outString) $key');
     }
   
  -  void _removeChild(UINode node) {
  +  void removeChild(UINode node) {
       _traceSync(_SyncOperation.REMOVAL, node._key);
       node._remove();
     }
  
positive.code:   String _key;
    UINode _parent;
    UINode get parent => _parent;
    RenderCSS _root;
    bool _defunct = false;
  
    UINode({ Object key }) {
  
negative.code:   void _sync(UINode old, dynamic slot) {
      UINode oldContent = old == null ? null : (old as ContentNode).content;
      content = _syncChild(content, oldContent, slot);
      assert(content.root != null);
      root = content.root;
    }
  
    void _remove() {
      if (content != null)
        removeChild(content);
      super._remove();
    }
  }
  