speculation-rules/prerender/local-storage.https.html

<!DOCTYPE html>
<title>Same-origin prerendering can access localStorage</title>
<meta name="variant" content="?target_hint=_self">
<meta name="variant" content="?target_hint=_blank">
<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>
<script src="resources/utils.js"></script>

<body>
<script>
setup(() => assertSpeculationRulesIsSupported());

promise_test(async t => {
  const uid1 = token();
  const uid2 = token();

  // A promise to wait until a prerendered page writes data with the "prerender"
  // key in the local storage.
  const write_promise = new Promise((resolve, reject) => {
    window.addEventListener("storage", event => {
      if (event.key !== 'prerender') {
        reject("wrong key");
      } else {
        resolve();
      }
    }, { once: true });
  });

  const rule_extras = {'target_hint': getTargetHint()};

  window.localStorage.setItem('initial', uid1);
  const {exec} = await create_prerendered_page(
      t, undefined, undefined, rule_extras);
  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');

  await write_promise;
  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>