chromium/third_party/blink/web_tests/external/wpt/soft-navigation-heuristics/softnav-after-lcp-paint.tentative.html

<!DOCTYPE HTML>
<html>
<head>
<meta charset="utf-8">
<title>Detect simple soft navigation.</title>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="/resources/testdriver.js"></script>
<script src="/resources/testdriver-vendor.js"></script>
<script src="resources/soft-navigation-helper.js"></script>
<link rel="stylesheet" type="text/css" href="/fonts/ahem.css" />
</head>
<body>
  <main id=main>
    <div>
      <a id=link><img src="/images/lcp-256x256.png"></a>
    </div>
  </main>
  <script>
    const link = document.getElementById("link");
    testSoftNavigation({
      addContent: async () => {
        let lcp_element_painted;
        const lcp_element_paint_promise = new Promise((r) => { lcp_element_painted = r; });
        // Add an LCP element, but have it be small enough to not trigger the
        // Soft Navigation heuristics.
        const p = addTextParagraphToMain("Lorem Ipsu", /*element_timing=*/"lcp");
        (new PerformanceObserver(list => {
          // Once the first element is fully painted:
          lcp_element_painted();
        })).observe({type: "element", buffered: true});
        await lcp_element_paint_promise;
        // Add a smaller element that gets us over that threshold.
        addTextParagraphToMain("m");
      },
      link: link,
      test: "Test that an image LCP followed by a smaller soft navigation LCP"
        + " properly queues an LCP entry, even when the soft navigation is"
        + " detected after the LCP."});
  </script>
</body>
</html>