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Test Info:

<!DOCTYPE html>
<meta charset=utf-8 />
<title>Event Timing only times certain types of trusted event.
<meta name="timeout" content="long">
<button id='button' onmousedown='mainThreadBusy(60)'
onfocus='mainThreadBusy(60)'>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>
let trustedClickStart;
function trustedClickAndBlockMain(id) {
trustedClickStart =;
return clickAndBlockMain(id);
function untrustedClickAndBlockMain(id) {
const target = document.getElementById(id);
// Block mainthread in the callback, as dispatchEvent() is a sync call.
target.dispatchEvent(new MouseEvent('mousedown'));
function trustedFocusAndBlockMain(id) {
const target = document.getElementById(id);
trustedFocusStart =;
// Block mainthread in the callback, as focus() is a sync call.
promise_test(function(t) {
assert_implements(window.PerformanceEventTiming, 'Event Timing is not supported.');
let observedMouseDown = false;
const observerPromise = new Promise(resolve => {
new PerformanceObserver(t.step_func(entryList => {
const observerCallbackTime =;
const mouseDowns = entryList.getEntriesByName('mousedown');
// Ignore cases in which there is no mousedown.
if (mouseDowns.length === 0)
assert_false(observedMouseDown, 'Got more than one callback with mousedown.');
assert_equals(mouseDowns.length, 1,
"Should only observe one mousedown entry. Instead, got these: " +
JSON.stringify(mouseDowns) + ".");
assert_equals(mouseDowns[0].name, 'mousedown',
"The observed entry should be a mousedown");
assert_less_than(mouseDowns[0].startTime, observerCallbackTime,
"The startTime should be before observerCallbackTime");
assert_greater_than(mouseDowns[0].startTime, trustedClickStart,
"The startTime should be after trustedClickStart");
observedMouseDown = true;
})).observe({ entryTypes: ['event'] });
// Untrusted event of a type event timing cares about.
// Trusted event of a type event timing doesn't cares about.
// Trusted event of a type event timing cares about.
const clickPromise = trustedClickAndBlockMain('button').then(wait);
return Promise.all([observerPromise, clickPromise]);
}, "Event Timing only times certain types of trusted event.");