event-timing/only-observe-firstInput.html

<!DOCTYPE html>
<html>
<meta charset=utf-8 />
<title>Event Timing: only observe the first input</title>
<button id='button'>Generate a 'click' event</button>
<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>

<script>
  /* Test:
     PerformanceObserver for first-input is registered
     Click 1
     Click 2
     Wait
     Expected result:
     PerformanceObserver should observe one and only one entry.
  */
  async_test(function(t) {
    assert_precondition(window.PerformanceEventTiming, 'Event Timing is not supported.');
    let hasObservedFirstInput = false;
    new PerformanceObserver(t.step_func((entryList) => {
        assert_false(hasObservedFirstInput);
        hasObservedFirstInput = true;
        const observedEntries = entryList.getEntries().filter(
            entry => entry.name === 'mousedown');
        assert_equals(observedEntries.length, 1);
        assert_equals(observedEntries[0].entryType, 'first-input');
        assert_equals(observedEntries[0].name, 'mousedown');
    })).observe({ entryTypes: ['first-input'] });
    on_event(window, 'load', () => {
      clickAndBlockMain('button').then(() => {
        clickAndBlockMain('button').then(wait).then( () => {
          // After some wait, the PerformanceObserver should have processed both clicks.
          // One and only one first-input entry should have been dispatched, so
          // |hasObservedFirstInput| should be true.
          t.step_timeout( () => {
            assert_true(hasObservedFirstInput);
            t.done();
          }, 10);
        });
      });
    });
  },
  "Event Timing: check first-input for a PerformanceObserver observing only first-input."
  );
</script>
</html>