chromium/third_party/blink/web_tests/intersection-observer/tracking-document.html

<!DOCTYPE html>
<script src="../resources/testharness.js"></script>
<script src="../resources/testharnessreport.js"></script>

<div id="root"></div>

<script>
test(function() {
  var observer = new IntersectionObserver((changes) => {}, {root: root});
  var doc = document.implementation.createDocument("", null);
  doc.appendChild(root);
}, "IntersectionObserver with root in a document that has no window does not crash.");
</script>