image-loading-lazy-in-scroller.html

<!DOCTYPE html>
<link rel="help" href="https://html.spec.whatwg.org/#lazy-load-root-margin">
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>

<style>
  #scroller {
    width: 100px;
    height: 100px;
    overflow: scroll;
    background-color: gray;
  }

  #spacer {
    width: 130px;
    height: 130px;
  }

  #target {
    width: 100px;
    height: 100px;
  }
</style>

<div id="scroller">
  <div id="spacer"></div>
  <img
    id="target"
    src="resources/green.png"
    loading="lazy"
    onload="img_onload();"
  >
</div>

<script>
  const t = async_test(
    "Test that lazy-loaded images load when near viewport."
  );

  function img_onload() {
    t.done();
  }

  t.step_timeout(() => {
    t.unreached_func(
      "Timed out while waiting for image to load."
    )();
  }, 2000);
</script>

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