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

<!--
@BLINK-ALLOW:description*
@BLINK-ALLOW:htmlTag*
@WIN-ALLOW:description*
@AURALINUX-ALLOW:description*
@MAC-ALLOW:AXRoleDescription
@MAC-ALLOW:AXHelp
@UIA-WIN-ALLOW:FullDescription*
-->
<!DOCTYPE html>
<html>
<body>
  <details>
    <summary>details tag</summary>
    <p>The details tag specifies additional details that the user can view or hide on demand.</p>
  </details>

  <!-- If there is already a name on the <summary>, the contents become a description -->
  <details>
    <summary aria-label="name">details #2</summary>
    <p>Paragraph#2</p>
  </details>
</body>
</html>