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chromium/content/test/data/accessibility/html/heading.html 

<!--
@BLINK-ALLOW:hierarchicalLevel*
@MAC-ALLOW:AXDisclosureLevel
@WIN-ALLOW:level:*
@WIN-ALLOW:xml-roles*
@AURALINUX-ALLOW:level:*
@AURALINUX-ALLOW:xml-roles*
-->
<!DOCTYPE html>
<html>
<body>
  <h1>Heading 1</h1>
  <h2>Heading 2</h2>
  <h3>Heading 3</h3>
  <h4>Heading 4</h4>
  <h5>Heading 5</h5>
  <h6>Heading 6</h6>
</body>
</html>