chromium/content/test/data/accessibility/display-locking/activatable.html

<!--
@BLINK-ALLOW:offscreen
@BLINK-ALLOW:focus*
-->
<div>
  <div id=spacer style="height: 30000px"></div>
  <div id="locked" style="content-visibility: auto">
    <div>child</div>
    <div id="nested" style="content-visibility: auto">
      nested locked element!
      <button>locked button</button>
    </div>
    <div id="nonActivatable" style="content-visibility: hidden">
      nested non activatable locked element
      <button>locked button</button>
    </div>
  </div>
</div>