speculation-rules/prerender/resources/iframe-added-post-activation.html

<!doctype html>

<title>iframe added post activation: initiator and prerendered page</title>
<script src="/common/get-host-info.sub.js"></script>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="utils.js"></script>
<body>
<script>

// When loaded without the "?prerendering" param, this document is called the
// "intiator page". It starts a prerender to the same URL, but with the
// "?prerendering" param.
//
// When loaded with the "?prerendering" param, this document is the "prerendered
// page". It tells the initiator page when it is ready to activate, and messages
// the main test page when it is finished.

// main() runs the logic of the prerendered page.
//
// On activation, adds an iframe and tests its document.prerendering state.
async function main() {
  const activated = new Promise((resolve, reject) => {
    document.addEventListener('prerenderingchange', (e) => {
      const iframe = document.createElement('iframe');
      document.body.appendChild(iframe);
      resolve(iframe.contentDocument.prerendering)
    });
  });

  // Ask to activate.
  const prerenderChannel = new PrerenderChannel('prerender-channel');
  prerenderChannel.postMessage('readyToActivate');

  // Check that document.prerendering is false in the iframe.
  const iframePrerendering = await activated;
  assert_true(iframePrerendering === false,
              'document.prerendering in iframe should be false');
}

// See comment at the top of this file.
const params = new URLSearchParams(location.search);
const isPrerendering = params.has('prerendering');
if (!isPrerendering) {
  loadInitiatorPage();
} else {
  // For the prerendering page, run main() then message the test page with the
  // result.
  const testChannel = new PrerenderChannel('test-channel');
  main().then(() => {
    testChannel.postMessage('PASS');
  }).catch((e) => {
    testChannel.postMessage('FAIL: ' + e);
  });
}
</script>
</body>