mapTree method
Implementation
bool mapTree(DOMNode domRoot, T root) {
  if (root == null) return false;
  map(domRoot, root);
  if (domRoot is TextNode) return false;
  var domNodes = domRoot.nodes.toList();
  var nodes = domGenerator.getElementNodes(root);
  var limit = Math.min(domNodes.length, nodes.length);
  for (var i = 0; i < limit; i++) {
    var domNode = domNodes[i];
    var node = nodes[i];
    if (domGenerator.isEquivalentNode(domNode, node)) {
      mapTree(domNode, node);
    }
  }
  return true;
}