ndow whose iframe contains [normal page, srcdoc] entries.
  const w = await openWindow("../../resources/has-iframe.html", t);
  const iframe = w.document.querySelector("iframe");

  await waitToAvoidReplace(t);
  iframe.srcdoc = srcdocThatPostsParentOpener("srcdoc1");
  await waitForMessage(iframe.contentWindow);

  assert_equals(w.history.length, 2);

  // Now navigate to a different srcdoc
  iframe.srcdoc = srcdocThatPostsParentOpener("srcdoc2");

  // Test that it's a replace.
  await waitForMessage(ifra