anchor.diff:  
     String _class;
   
  -  WrapperNode({
  +  SkyElementWrapper({
       Object key,
       List<UINode> children,
       this.style,
  
positive.code:     }
    }
  
    void _syncNode(RenderNode old) {
      WrapperNode oldWrapperNode = old as WrapperNode;
      sky.Element root = _root as sky.Element;
  
      _ensureClass();
      if (_class != oldWrapperNode._class && _class != '')
        root.setAttribute('class', _class);
  
      if (inlineStyle != oldWrapperNode.inlineStyle)
        root.setAttribute('style', inlineStyle);
  
      _syncChildren(oldWrapperNode);
    }
  
    void _syncChildren(WrapperNode oldWrapperNode) {
      sky.Element root = _root as sky.Element;
      assert(root != null);
  
      var startIndex = 0;
      var endIndex = children.length;
  
      var oldChildren = oldWrapperNode.children;
      var oldStartIndex = 0;
      var oldEndIndex = oldChildren.length;
  
  
negative.code: 
  final List<UINode> _emptyList = new List<UINode>();
  
  abstract class SkyElementWrapper extends SkyNodeWrapper {
  
    String get _tagName;
  
  