android_webview/test/data/prerender.html

<html>
  <body>
  </body>
  <script src="prerender-test-setup.js"></script>
  <script>
    // Objects starting with the "aw" prefix are injected by AwPrerenderTest.

    const params = new URLSearchParams(document.location.search);
    const iframeSrc = params.get("iframeSrc");
    if (iframeSrc !== null) {
      createIframe(iframeSrc);
    }

    // Post a message to Java (AwPrerenderTest.java). This should be deferred
    // until activation.
    awDeferredMessagePort.postMessage(
        wasPrerendered ? "Prerendered" : "Not prerendered");
    // Notify Java that the message was posted. This notification should not be
    // deferred even during prerendering.
    awPostMessageFuture.done();
  </script>
</html>