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Test Info:

<!DOCTYPE HTML>
<meta charset=utf-8>
<title>Largest Contentful Paint: observe image.</title>
<body>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="resources/largest-contentful-paint-helpers.js"></script>
<script>
async_test(function (t) {
assert_implements(window.LargestContentfulPaint, "LargestContentfulPaint is not implemented");
const beforeLoad = performance.now();
const observer = new PerformanceObserver(
t.step_func_done(function(entryList) {
assert_equals(entryList.getEntries().length, 1);
const entry = entryList.getEntries()[0];
const url = window.location.origin + '/images/blue.png';
// blue.png is 133 by 106.
const size = 133 * 106;
checkImage(entry, url, 'image_id', size, beforeLoad);
})
);
observer.observe({type: 'largest-contentful-paint', buffered: true});
}, 'Same-origin image after a JS initiated scroll event is observable.');
document.body.dispatchEvent(new Event('scroll'));
const image = new Image();
image.id = 'image_id';
image.src = '/images/blue.png';
document.body.appendChild(image);
</script>
</body>