chromium/third_party/blink/web_tests/external/wpt/event-timing/event-retarget.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>

<script src=resources/event-timing-test-utils.js></script>

<custom-button id='custom_button'></custom-button>

<script>
async_test(function(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').onclick = () => {
        innerButtonClicked = true;
      };
    }
  });
  const observer = new PerformanceObserver(t.step_func((entryList) => {
    const entries = entryList.getEntriesByName('pointerdown');
    if (entries.length === 0)
      return;

    // There must only be one pointerdown entry.
    assert_equals(entries.length, 1);
    verifyClickEvent(entries[0], 'custom_button', true);
    assert_true(innerButtonClicked);
    t.done()
  }));
  observer.observe({entryTypes: ['event']});
  clickAndBlockMain('custom_button');
}, "Event Timing: target reports the last Event Target, i.e. nothing from shadow DOM.");
</script>
</html>