iframe-loading-lazy-in-scroller-horizontal-far.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;
    display: flex;
  }

  #spacer {
    width: 10000vw;
    height: 130px;
    flex-shrink: 0;
  }

  #target {
    width: 100px;
    height: 100px;
    flex-shrink: 0;
  }
</style>

<div id="scroller">
  <div id="spacer"></div>
  <iframe
    id="target"
    src="resources/subframe.html"
    loading="lazy"
    onload="iframe_onload();"
  ></iframe>
</div>

<script>
  const t = async_test(
    "Test that lazy-loaded iframes do not load when far from viewport."
  );

  function img_onload() {
    t.unreached_func(
      "Lazy-loading iframe far from viewport should not load."
    )();
  }

  t.step_timeout(() => {
    t.done();
  }, 2000);
</script>

chromium/third_party/blink/web_tests/external/wpt/html/semantics/embedded-content/the-iframe-element/iframe-loading-lazy-in-scroller-horizontal-far.html