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chromium/content/test/data/accessibility/event/live-region-add-live-attribute.html 

<!--
@UIA-WIN-DENY:*
@UIA-WIN-ALLOW:AriaProperties*
@UIA-WIN-ALLOW:LiveRegion*
@UIA-WIN-ALLOW:LiveSetting*
-->
<!DOCTYPE html>
<html>
<body>
<p id="live">Live region</p>
<script>
  function go() {
    var p = document.getElementById('live');
    p.setAttribute('aria-live', 'polite');
  }
</script>
</body>
</html>