chromium/third_party/blink/web_tests/external/wpt/serial/resources/open-in-iframe.html

<!DOCTYPE html>

<script src="/resources/testdriver.js"></script>
<script src="/resources/testdriver-vendor.js"></script>

<body>
  <button>Fake user gesture</button>
</body>

<script>
  'use strict';

  test_driver.set_test_context(parent);

  window.onmessage = messageEvent => {
    switch (messageEvent.data.type) {
      case 'GetPorts':
        navigator.serial.getPorts()
            .then(ports => parent.postMessage('Success', '*'))
            .catch(err => parent.postMessage(`FAIL: ${err}`, '*'));
        break;
      case 'RequestPort':
        test_driver.click(document.getElementsByTagName('button')[0])
            .then(() => navigator.serial.requestPort({filters: []}))
            .then(port => parent.postMessage('Success', '*'))
            .catch(err => parent.postMessage(`FAIL: ${err}`, '*'));
        break;
      default:
        parent.postMessage(
            `FAIL: Bad message type: ${messageEvent.data}`, '*');
    };
  };
</script>