chromium/third_party/blink/web_tests/external/wpt/service-workers/service-worker/data-transfer-files.https.html

<!DOCTYPE html>
<meta charset="utf-8">
<title>Post a file in a navigation controlled by a service worker</title>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="resources/test-helpers.sub.js"></script>
<body>
<iframe id=testframe name=testframe></iframe>
<form id=testform method=post action="/html/semantics/forms/form-submission-0/resources/file-submission.py" target=testframe enctype="multipart/form-data">
<input name=testinput id=testinput type=file>
</form>
<script>
// Test that DataTransfer with a File entry works when posted to a
// service worker that falls back to network. Regression test for
// https://crbug.com/944145.
promise_test(async (t) => {
  const scope = '/html/semantics/forms/form-submission-0/resources/';
  const header = `pipe=header(Service-Worker-Allowed,${scope})`;
  const script = `resources/fetch-event-network-fallback-worker.js?${header}`;

  const registration = await service_worker_unregister_and_register(
      t, script, scope);
  await wait_for_state(t, registration.installing, 'activated');

  const dataTransfer = new DataTransfer();
  dataTransfer.items.add(new File(['foobar'], 'name'));
  assert_equals(1, dataTransfer.files.length);

  testinput.files = dataTransfer.files;
  testform.submit();

  const data = await new Promise(resolve => {
    onmessage = e => {
      if (e.source !== testframe) return;
      resolve(e.data);
    };
  });
  assert_equals(data, "foobar");
}, 'Posting a File in a navigation handled by a service worker');
</script>
</body>