event-timing/first-input-shadow-dom.html

<!DOCTYPE html>
<html>
<meta charset=utf-8 />
<script src=/resources/testharness.js></script>
<script src=/resources/testharnessreport.js></script>
<script src=/resources/testdriver.js></script>
<script src=/resources/testdriver-vendor.js></script>

<body>
<div id='container'>
  <custom-button id='custom_button'></custom-button>
</div>
<script>
promise_test(t => {
  assert_implements(window.PerformanceEventTiming, 'Event Timing is not supported.');
  let innerButtonClicked = false;
  customElements.define('custom-button', class extends HTMLElement {
    connectedCallback() {
      this.attachShadow({mode: 'open'});
      this.shadowRoot.innerHTML = `<button id='inner_button_id'>Click me</button>`;
      this.shadowRoot.getElementById('inner_button_id').onpointerdown = () => {
        innerButtonClicked = true;
      };
    }
  });
  const observerPromise = new Promise(resolve => {
    new PerformanceObserver(t.step_func(entryList => {
      // There must only be one first-input entry.
      assert_equals(entryList.getEntries().length, 1);
      // entry.target must be the shadow host due to retargetting.
      assert_equals(entryList.getEntries()[0].target,
          document.getElementById('custom_button'));
      assert_true(innerButtonClicked, 'Did not reach the shadow DOM event listener!');
      resolve();
    })).observe({entryTypes: ['first-input']});
  });
  const clickPromise = test_driver.click(document.getElementById('custom_button'));
  return Promise.all([observerPromise, clickPromise]);
}, "Event Timing: test first input on shadow DOM.");
</script>
</body>
</html>