function assertNodeIsElement(node) {
  if (googAsserts.ENABLE_ASSERTS && !isNodeElement(node)) {
    googAsserts.fail(
        'Expected Node of type Element but got Node of type %s',
        getNodeType(node));
  }
  return /** @type {!Element} */ (node);
}
Asserts that a Node is an Element, without falling prey to things like
<form><input name="nodeType"></form>.
@param {!Node} node
@return {!Element}