chromium/third_party/blink/web_tests/external/wpt/shared-storage/resources/shared-storage-writable-img-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() {
  // Create image that sets (expectedKey, expectedValue) to shared storage
  // via response header.
  let {expectedKey, expectedValue} = parseExpectedKeyAndValueData();
  const imgSrc =
    `/shared-storage/resources/shared-storage-writable-pixel.png`
    + `?key=${expectedKey}&value=${expectedValue}`;
  let image = document.createElement('img');
  image.src = imgSrc;
  image.sharedStorageWritable = true;

  let parentOrOpener = window.opener || window.parent;
  const promise = new Promise((resolve, reject) => {
    image.addEventListener('load', () => {
      parentOrOpener.postMessage({sharedStorageImageLoadStatus: "success"}, "*");
      resolve();
    });
    image.addEventListener('error', () => {
      parentOrOpener.postMessage({sharedStorageImageLoadStatus: error}, "*");
      reject(error);
    });
  });

  // Navigate and wait for image load.
  document.body.appendChild(image);
  await promise;
}

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