<!DOCTYPE html>
This test passes if it does not crash.
<script>
  var doc1 = document.documentElement;
  let iframe1 = document.createElement("iframe");
  doc1.appendChild(iframe1);
  separateDoc = document.implementation.createDocument("", null);
  iframe1.addEventListener("DOMFocusOut", function () {  separateDoc.adoptNode(iframe1); });
  iframe1.focus();
  iframe1 = document.createElement("iframe");
  doc1.appendChild(iframe1);
  iframe1.focus();
</script>
