 test that the worker script started correctly and message passing
  // is enabled.
  filtered_registrations[0].active.postMessage({type: 'test_message'});
  const msg1 = await next_message();
  assert_true(msg1.ok, 'Message passing');

  // Test that the partitioned cookie is not available to this worker via HTTP.
  filtered_registrations[0].active.postMessage({type: 'echo_cookies_http'});
  const msg2 = await next_message();
  assert_true(msg2.ok, 'Get cookies');
  assert_false(
      msg2.cookies.include