speculation-rules/prerender/local-storage.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 uid1 = token();
  const uid2 = token();
  window.localStorage.setItem('initial', uid1);
  const {exec} = await create_prerendered_page(t);
  const result = await exec(uid2 => {
    window.localStorage.setItem('prerender', uid2);
    return window.localStorage.getItem('initial');
  }, [uid2])

  // Start prerendering a page that attempts to access localStorage API.
  assert_equals(
    result, uid1,
      'prerendering page should be able to read from local storage');
  assert_equals(
      window.localStorage.getItem('prerender'), uid2,
      'prerendering page should be able to write to local storage');
}, 'prerendering page should be able to access local storage');

</script>
</body>