chromium/content/test/data/accessibility/event/input-combobox-aria1.html

<!-- Simple aria-1.0 combobox test html for end-to-end a11y unit tests. -->
<html>
  <head>
    <script>
      function go() {
        document.getElementById('test-input').focus();
        document.getElementById('test-input').setAttribute('aria-expanded', 'true');
        document.getElementById('test-listbox').removeAttribute('hidden');
        document.getElementById('test-input').setAttribute('aria-controls', 'test-listbox');
      }
    </script>
  </head>
  <body>
    <input id="test-input" type="text" role="combobox" aria-expanded="false">
    <ul id="test-listbox" role="listbox" hidden>
      <li role="option">Chrome</li>
      <li role="option">Chromium</li>
      <li role="option">Clank</li>
    </ul>
  </body>
</html>