chromium/chrome/test/data/private_network_access/remote-initiator-navigation.html

<html>
  <head>
    <!-- Disable extra network request for /favicon.ico -->
    <link rel="icon" href="data:,">

    <script>
      // Adds an <iframe> child to `doc` with the given `src` attribute.
      // Waits when the child has loaded, then returns the child.
      function addChildFrame(doc, src) {
        return new Promise(resolve => {
          const child = doc.createElement("iframe");
          child.src = src;
          child.addEventListener("load", () => resolve(child));
          doc.body.appendChild(child);
        });
      }

      // Opens a new window to `src`, waits for it to load, then returns it.
      function openWindow(src) {
        return new Promise(resolve => {
          openee = window.open(src);
          openee.addEventListener("load", () => resolve(openee));
        });
      }

      // Runs a test:
      //
      // - Embeds a new `about:blank` iframe
      // - Opens a new window to a document in the `public` address space
      // - Has the new window navigate the child iframe to `url`, then do
      //   something specified by `initiatorBehavior` immediately after
      //
      // `initiatorBehavior` can be:
      //
      // - "close": the new window closes itself
      // - "navigate": the new window navigates itself to a new document
      // - anything else: the new window does nothing
      //
      function runTest({ url, initiatorBehavior }) {
        return new Promise(async (resolve) => {
          window.mainChild = await addChildFrame(document, "about:blank");
          window.mainChild.addEventListener("load", () => resolve(true));

          // Navigate `mainChild` from a new window in the `public` address
          // space, then wait until `mainChild` has finished loading.

          openee = await openWindow(
              "/private_network_access/navigate-opener-child.html");

          openee.postMessage({ url, initiatorBehavior }, "*");
        });
      }
    </script>
  </head>
  <body></body>
</html>