  (e.g. table, select) in lieu of native CE type extensions without
  //     massive new invention in this space (e.g. directive system)
  const templateExtensions = {
    'dom-if': true,
    'dom-repeat': true
  };
  function wrapTemplateExtension(node) {
    let is = node.getAttribute('is');
    if (is && templateExtensions[is]) {
      let t = node;
      t.removeAttribute('is');
      node = t.ownerDocument.createElement(is);
      t.parentNode.replaceChild(node, t);
      node.appendChild(t);
      whi