anchor.diff:    }
   }
   
  -class Container extends WrapperNode {
  +class Container extends SkyElementWrapper {
   
     String get _tagName => 'div';
   
     static final Container _emptyContainer = new Container();
   
  -  RenderNode get _emptyNode => _emptyContainer;
  +  SkyNodeWrapper get _emptyNode => _emptyContainer;
   
     Container({
       Object key,
  
positive.code:       }
  
        UINode parent = _parent;
        while (parent != null && parent is! RenderNode) {
          if (parent is StyleNode && (parent as StyleNode).style != null)
            styles.add((parent as StyleNode).style);
  
  
negative.code: }
  
  /*
   * SkyNodeWrappers correspond to a desired state of a sky.Node. They are fully
   * immutable, with one exception: A UINode which is a Component which lives within
   * an SkyElementWrapper's children list, may be replaced with the "old" instance if it
   * has become stateful.
   */
  abstract class SkyNodeWrapper extends UINode {
  
    static final Map<sky.Node, SkyNodeWrapper> _nodeMap =
        new HashMap<sky.Node, SkyNodeWrapper>();
  
    static SkyNodeWrapper _getMounted(sky.Node node) => _nodeMap[node];
  
    SkyNodeWrapper({ Object key }) : super(key: key);
  
    SkyNodeWrapper get _emptyNode;
  
    sky.Node _createNode();
  
  