speculation-rules/prerender/fetch-blob.html

<!DOCTYPE html>
<title>Same-origin prerendering can access localStorage</title>
<meta name="timeout" content="long">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="/common/utils.js"></script>
<script src="/common/dispatcher/dispatcher.js"></script>
<script src="resources/utils.js"></script>
<body>
<script>

setup(() => assertSpeculationRulesIsSupported());

promise_test(async t => {
  const {exec} = await create_prerendered_page(t);
  const result = await exec(async () => {
    const blob = await (await fetch('cache.txt')).blob();
    const reader = new FileReader();
    reader.readAsText(blob);
    return new Promise(function(resolve, reject) {
      reader.onload = () => resolve(reader.result);
      reader.onerror = () => reject(reader.error);
    });
  });
  const expected = "Hello, Prerender API!";

  // Start prerendering a page that attempts to access the blob.
  assert_equals(
    result, expected,
    'prerendering page should be able to read from blobs.');
}, 'prerendering page should be able to access blobs');

</script>
</body>