chromium/third_party/blink/web_tests/external/wpt/selection/shadow-dom/cross-shadow-boundary-select-document.html

<!doctype html>
<html>
  <head>
    <link rel=match href="cross-shadow-boundary-select-document-ref.html">
  </head>
  <div></div>
  <script>
    const root = document.querySelector("div").attachShadow({mode: "open"});
    root.innerHTML = "CONTENT";
    getSelection().setBaseAndExtent(document, 0, root.firstChild, 2);
  </script>
</html>