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diff --git a/testing/web-platform/tests/largest-contentful-paint/observe-after-untrusted-scroll.html b/testing/web-platform/tests/largest-contentful-paint/observe-after-untrusted-scroll.html
new file mode 100644
index 0000000000..c84f922e5e
--- /dev/null
+++ b/testing/web-platform/tests/largest-contentful-paint/observe-after-untrusted-scroll.html
@@ -0,0 +1,32 @@
+<!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>