chromium/third_party/blink/web_tests/external/wpt/document-picture-in-picture/focus-opener.https.html

<!DOCTYPE html>
<title>Test that a document picture-in-picture window can use Window's focus()
  API to focus its opener window</title>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="/resources/testdriver.js"></script>
<script src="/resources/testdriver-vendor.js"></script>
<body>
  <iframe></iframe>
<script>
promise_test(async (t) => {
  await test_driver.bless('request PiP window from top window');
  const pipWindow = await documentPictureInPicture.requestWindow();

  // Blur this window by focusing the iframe. This will allow us to detect that
  // the document picture-in-picture window has focused us.
  const blurPromise = new Promise(async (resolve) => {
    window.addEventListener('blur', resolve, { once: true });
    await test_driver.bless('focus inner iframe to blur window');
    document.getElementsByTagName('iframe')[0].focus();
  });
  await blurPromise;

  // Now focus this window from the document picture-in-picture window's
  // context.
  const focusPromise = new Promise(async (resolve) => {
    window.addEventListener('focus', resolve, { once: true });
    await test_driver.bless('focus opener window', pipWindow);
    const focusScript = pipWindow.document.createElement('script');
    focusScript.setAttribute('src', 'support/focus-opener.js');
    pipWindow.document.body.append(focusScript);
  });
  return focusPromise;
});
</script>
</body>