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<!DOCTYPE html>
<html class="hide">
<head>
<title>Performance Paint Timing Test: Text FCP due to the documentElement's opacity</title>
<style>
html {
will-change: opacity;
}
.hide {
opacity: 0;
}
</style>
</head>
<body>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="../resources/utils.js"></script>
<div id="main">This is content that is extremely contentful.</div>
<script>
const change_opacity = () => {
document.documentElement.className = "";
}
promise_test(async t => {
assert_implements(window.PerformancePaintTiming, "Paint Timing isn't supported.");
await assertNoFirstContentfulPaint(t);
change_opacity();
await waitForAnimationFrames(3);
const fcp_entries = performance.getEntriesByName('first-contentful-paint');
assert_equals(fcp_entries.length, 1, "Got an FCP entry");
const lcp_entries = await new Promise(resolve => {new PerformanceObserver((list) => resolve(list.getEntries())).observe({type: 'largest-contentful-paint', buffered: true})});
assert_equals(lcp_entries.length, 1, "Got an LCP entry");
assert_less_than_equal(fcp_entries[0].startTime, lcp_entries[0].startTime, "LCP is not smaller than FCP");
}, "Test that FCP after opacity change is not a larger value than LCP");
</script>
</body>
</html>
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