observe-after-untrusted-scroll.html

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This WPT test may be referenced by the following Test IDs:
- /largest-contentful-paint/observe-after-untrusted-scroll.html - WPT Dashboard Interop Dashboard

<!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>