chromium/content/test/data/accessibility/html/combobox-optgroup.html

<!--
@MAC-ALLOW:AXRoleDescription
@WIN-ALLOW:xml-roles*
@WIN-ALLOW:IA2_STATE_VERTICAL
@WIN-ALLOW:SELECTABLE
@UIA-WIN-ALLOW:Value.IsReadOnly*
@BLINK-ALLOW:setSize*
@BLINK-ALLOW:posInSet*
@AURALINUX-ALLOW:xml-roles*
@AURALINUX-ALLOW:posinset*
@AURALINUX-ALLOW:setsize*
@AURALINUX-ALLOW:enabled
-->
<!DOCTYPE html>
<html>

<body>

  <select>
    <optgroup label="Swedish Cars" aria-label="Swedish Cars Label">
      <option value="volvo" aria-label="Volvo Label">Volvo</option>
      <option value="saab" aria-label="Saab Label">Saab</option>
    </optgroup>
    <optgroup label="German Cars">
      <option selected value="mercedes" aria-label="Mercedes Label">Mercedes</option>
      <option value="audi" aria-label="Audi Label">Audi</option>
    </optgroup>
  </select>

</body>

</html>