chromium/third_party/blink/web_tests/external/wpt/css/css-scroll-anchoring/support/history-restore-anchors-new-window.html

<style>
  body {
    margin: 0px;
    height: 2000px;
    width: 2000px;
  }

  #first {
    height: 1000px;
    background-color: #FFA5D2;
  }

  #anchor {
    position: absolute;
    background-color: #84BE6A;
    height: 600px;
    width: 100%;
  }
</style>

<div id="first"></div>
<div id="changer"></div>
<div id="anchor"></div>

<script>
onload = function() {
  opener.postMessage("loaded", "*");
}
</script>