chromium/third_party/blink/web_tests/external/wpt/html/semantics/embedded-content/the-img-element/image-loading-eager.html

<!DOCTYPE html>
<head>
  <title>Images with loading='eager' load immediately regardless of their
         position with respect to the viewport</title>
  <link rel="author" title="Scott Little" href="mailto:[email protected]">
  <link rel="help" href="https://github.com/scott-little/lazyload">
  <script src="/resources/testharness.js"></script>
  <script src="/resources/testharnessreport.js"></script>
</head>

<script>
  const t = async_test("Test that images with loading='eager' load " +
                       "immediately regardless of their position with " +
                       "respect to the viewport.");

  let has_in_viewport_loaded = false;
  const in_viewport_img_onload = t.step_func(() => {
    assert_false(has_in_viewport_loaded,
                 "The in_viewport element should load only once.");
    has_in_viewport_loaded = true;
  });

  let has_below_viewport_loaded = false;
  const below_viewport_img_onload = t.step_func(() => {
    assert_false(has_below_viewport_loaded,
                 "The below_viewport element should load only once.");
    has_below_viewport_loaded = true;
  });

  window.addEventListener("load", t.step_func_done(() => {
    assert_true(has_in_viewport_loaded,
                "The in_viewport element should have loaded before window.load().");
    assert_true(has_below_viewport_loaded,
                "The below_viewport element should have loaded before window.load().");
  }));

</script>

<body>
  <img id="in_viewport" src="resources/image.png?in-viewport" loading="eager" onload="in_viewport_img_onload();">
  <div style="height:10000px;"></div>
  <!-- The below_viewport element loads very slowly in order to ensure that the
       window load event is blocked on it. -->
  <img id="below_viewport"
       src="resources/image.png?below-viewport&pipe=trickle(d2)"
       loading="eager" onload="below_viewport_img_onload();">
</body>