anchor.diff:  
     // A function that is called when this tree needs to be rendered
     // into the DOM.
  -  RenderFunction renderFunction;
  +  final RenderFunction renderFunction;
   
     // The actual rendered row.
     TreeTableRow rowElement;
  
positive.code:     open = !open;
      if (open) {
        if (children.isEmpty) {
          children = generatorFns.map((a) => a()).toList();
          // Resort because more children were generated.
          sort(sortComparator);
        }
  
negative.code:   HtmlElement parentElement;
  
    // The depth of this row in the overall tree.
    final int level;
  
    // Stored comparator for the sorting function.
    // Because the tree is generated lazily, this needs to be stored to
  