chromium/third_party/blink/web_tests/external/wpt/shared-storage/resources/shared-storage-writable-fetch-request-in-sandboxed-iframe-inner.https.sub.html

<!doctype html>
<body>
  <script src=/resources/testharness.js></script>
  <script src=/shared-storage/resources/util.js></script>
  <script>

async function init() {
  // Make fetch request that sets (expectedKey, expectedValue) to shared storage
  // via response header.
  let {expectedKey, expectedValue} = parseExpectedKeyAndValueData();
  const rawWriteHeader = `set;key=${expectedKey};value=${expectedValue}`;
  const writeHeader = encodeURIComponent(rawWriteHeader);
  const fetchUrl =
    `/shared-storage/resources/shared-storage-write-notify-parent.py` +
    `?write=${writeHeader}`;
  let frame = document.createElement('iframe');
  let parentOrOpener = window.opener || window.parent;
  fetch(fetchUrl, {sharedStorageWritable: true})
    .then(response => response.text())
    .then(htmlContent => {
        frame.srcdoc = htmlContent;

        const promise = new Promise((resolve, reject) => {
          window.addEventListener('message', async function handler(evt) {
            if (evt.source === frame.contentWindow &&
                evt.data.sharedStorageWritableHeader) {
              assert_equals(evt.data.sharedStorageWritableHeader, '?1');
                parentOrOpener.postMessage({
                    sharedStorageFetchStatus: "success",
                    sharedStorageWritableHeader:
                      evt.data.sharedStorageWritableHeader},
                                         "*");
              document.body.removeChild(frame);
              window.removeEventListener('message', handler);
              resolve();
            }
          });
          window.addEventListener('error', () => {
            reject(new Error('Fetch or navigation error'));
          });
        });

      // Navigate and wait for notification.
      document.body.appendChild(frame);
      return promise;
    })
    .catch(error => {
      parentOrOpener.postMessage({sharedStorageFetchStatus: error}, "*");
    });
}

init();
  </script>
</body>