servo/tests/wpt/web-platform-tests/largest-contentful-paint/image-src-change.html

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HTML

<!DOCTYPE HTML>
<meta charset=utf-8>
<title>Largest Contentful Paint: src change triggers new entry.</title>
<body>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="resources/largest-contentful-paint-helpers.js"></script>
<img src='/images/blue.png' id='image_id'/>
<script>
async_test(function (t) {
assert_implements(window.LargestContentfulPaint, "LargestContentfulPaint is not implemented");
let beforeLoad = performance.now();
let firstCallback = true;
const observer = new PerformanceObserver(
t.step_func(function(entryList) {
assert_equals(entryList.getEntries().length, 1);
const entry = entryList.getEntries()[0];
const url = window.location.origin + (firstCallback ? '/images/blue.png' : '/images/black-rectangle.png');
// blue.png is 133 by 106. black-rectangle.png is 100 x 50.
const size = firstCallback ? 133 * 106 : 100 * 50;
checkImage(entry, url, 'image_id', size, beforeLoad);
if (firstCallback) {
// Set the src to trigger another entry.
const img = document.getElementById('image_id');
img.src = '/images/black-rectangle.png';
beforeLoad = performance.now();
firstCallback =false;
} else {
t.done();
}
})
);
observer.observe({type: 'largest-contentful-paint', buffered: true});
}, 'Largest Contentful Paint: changing src causes a new entry to be dispatched.');
</script>
</body>