chromium/third_party/blink/renderer/core/testing/data/touch-action-shadow-dom.html

<!DOCTYPE html>
<link rel='stylesheet' type='text/css' href='touch-action-tests.css'>
<script src='touch-action-tests.js'></script>

<!-- 
     Test a bunch of cases involving shadow DOM.
-->
<div shadow-host></div>
<div make-shadow-dom>
  <div expected-action='auto'>
    Default touch-action is still auto inside shadow DOM
  </div>
</div>

<div shadow-host></div>
<div make-shadow-dom>
  <div class='ta-none' expected-action='none'>
    touch-action: none still applies inside shadow DOM
  </div>
</div>

<div class='ta-none' shadow-host></div>
<div make-shadow-dom>
  <div expected-action='none'>
    touch-action: none applies across shadow DOM boundary
  </div>
</div>

<div shadow-host>
  <div expected-action='none'>
    touch-action: none applies as part of projection
  </div>
</div>
<div make-shadow-dom>
  <div class='ta-none'>
    <content></content>
  </div>
</div>