message: fix(aio): remove es2015 syntax from the onerror webmaster tools debugger
diff: <script>
  window.onerror = function (message, url, lineNo, colNo, error) {
  - let container = document.createElement('div');
  + var container = document.createElement('div');
  container.style.color = 'red';
  container.style.position = 'fixed';
  container.style.top = '3em';
  container.style.left = '1em';
  - let msg = document.createElement('pre');
  + var msg = document.createElement('pre');
  msg.innerText = [
  'UA: ' + window.navigator.userAgent,
  'Message: ' + message,
  