chromium/content/test/data/accessibility/aom/aom-checked.html

<!DOCTYPE html>
<!--
@BLINK-ALLOW:checkedState=*
@MAC-ALLOW:AXRoleDescription
@WIN-ALLOW:CHECKED*
@WIN-ALLOW:MIXED*
@AURALINUX-DENY:checkable
@AURALINUX-ALLOW:checkable:*
-->
<html>
<body>
  <div role="checkbox" tabindex=0 id="c1"></div>
  <div role="checkbox" tabindex=0 id="c2"></div>
  <div role="checkbox" tabindex=0 id="c3"></div>
  <div role="checkbox" tabindex=0 id="c4"></div>
  <script>
    document.getElementById("c2").accessibleNode.checked = "true";
    document.getElementById("c3").accessibleNode.checked = "false";
    document.getElementById("c4").accessibleNode.checked = "mixed";
  </script>
</body>
</html>