anchor.diff:          return false;
   
         oldNodeIdMap[currentNode._key] = null; // mark it reordered
  -      assert(_root is RenderCSSContainer);
  -      assert(oldNode._root is RenderCSSContainer);
  -
  -      old._root.remove(oldNode._root);
  -      _root.add(oldNode._root, before: nextSibling);
  +      assert(root is RenderCSSContainer);
  +      assert(oldNode.root is RenderCSSContainer);
  +
  +      old.root.remove(oldNode.root);
  +      root.add(oldNode.root, before: nextSibling);
   
         return true;
       }
   
       // Scan forwards, this time we may re-order;
  -    nextSibling = _root.firstChild;
  +    nextSibling = root.firstChild;
       while (startIndex < endIndex && oldStartIndex < oldEndIndex) {
         currentNode = children[startIndex];
         oldNode = oldChildren[oldStartIndex];
   
         if (currentNode._key == oldNode._key) {
           assert(currentNode.runtimeType == oldNode.runtimeType);
  -        nextSibling = _root.childAfter(nextSibling);
  +        nextSibling = root.childAfter(nextSibling);
           sync(startIndex);
           startIndex++;
           advanceOldStartIndex();
  
positive.code: 
  class Container extends OneChildListRenderNodeWrapper {
  
    RenderCSSContainer _root;
    RenderCSSContainer _createNode() => new RenderCSSContainer(this);
  
    static final Container _emptyContainer = new Container();
  
    RenderNodeWrapper get _emptyNode => _emptyContainer;
  
    Container({
      Object key,
  
negative.code:       return;
  
      _trace('$_key rebuilding...');
      assert(root != null);
      _sync(null, _slot);
    }
  
  