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Test Info: Warnings

<!DOCTYPE html>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
@font-face {
font-family: 'TestFaceSmaller';
src: url('/fonts/CSSTest/csstest-basic-regular.ttf?pipe=trickle(d0.5)');
size-adjust: 30%;
font-display: swap;
.test {
font-family: 'TestFaceSmaller';
Web-font styled text that gets resized during swap period should not make a
LCP emission if the new size is smaller than the current LCP element size.
<div class="test">LCP: Web Font Styled Text Resize</div>
function LCPEntryList(t) {
return new Promise(resolve => {
let = lcpEntries = [];
new PerformanceObserver((entryList, observer) => {
lcpEntries = lcpEntries.concat(entryList.getEntries());
if (lcpEntries) {
// Adding timeout to wait a bit more so that if there are more than
// expected LCP entries emitted, they can be observed.
t.step_timeout(() => {
}, 200);
}).observe({ type: 'largest-contentful-paint', buffered: true });
promise_test(async t => {
await document.fonts.ready;
// Verify web font is loaded.
assert_own_property(window, 'PerformanceResourceTiming', "ResourceTiming not supported");
let url = '/fonts/CSSTest/csstest-basic-regular.ttf?pipe=trickle(d0.5)';
var absoluteURL = new URL(url, location.href).href;
assert_equals(performance.getEntriesByName(absoluteURL).length, 1, 'Web font should be downloaded');
// Verify web font is available.
assert_true(document.fonts.check('10px TestFaceSmaller'), 'Font should be the web font added');
// Verify there is only one LCP entry.
let entryList = await LCPEntryList(t);
assert_equals(entryList.length, 1, 'Web font styled text resize that occurs during swap period but is smaller should not make a new LCP emission.')
}, "LCP should be not updated if the web font styled text resizes to be smaller during the swap period");