chromium/third_party/blink/web_tests/external/wpt/soft-navigation-heuristics/image-lcp-before-detection.tentative.html

<!DOCTYPE HTML>
<html>
<head>
<meta charset="utf-8">
<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>
</head>
<body>
  <main id=main>
    <div>
      <a id=link><img src="/images/lcp-256x256.png" id="img"></a>
    </div>
  </main>
  <script>
    const link = document.getElementById("link");
    let first_lcp_painted;
    let second_lcp_painted;
    (async () => {
      await new Promise(r => { first_lcp_painted = r; });
      addImageToMain("lcp-133x106.png", "no_lcp");
      (new PerformanceObserver(second_lcp_painted)).observe({type: "element"});
    })();
    testSoftNavigation({
      pushState: null,
      addContent: async () => {
        // Add an LCP element.
        await new Promise(resolve => {
          addImageToMain("lcp-100x50.png", "first_lcp");
          (new PerformanceObserver(resolve)).observe({type: "element"});
        });
        first_lcp_painted();
        // Wait for the unrelated LCP to be painted.
        await new Promise(r => { second_lcp_painted = r; });
        const url = URL + "?" + counter;
        history.pushState({}, '', url);
      },
      link: link,
      validate: async () => {
        const lcps = await getLcpEntries();
        assert_equals(lcps.length, 2, "Got 2 LCP entries");
        assert_equals(lcps[lcps.length - 1].id, "first_lcp", "Got the first LCP");
      },
      test: "Image LCP discovered between user interaction and soft " +
            "navigation detection are properly reported, while unrelated " +
            "LCPs are ignored during that time. As a side effect, we also " +
            "test element timing."});
  </script>
</body>
</html>