Codebase Browser
chromium
Go to App

chromium/content/test/data/accessibility/event/tabindex-added-on-aria-hidden.html 

<!DOCTYPE html>
<html>
<body>
<div id="d" aria-hidden="true"></div>
<script>
  function go() {
    document.querySelector('#d').tabIndex = 0;
  }
</script>
</body>
</html>