chromium/third_party/blink/web_tests/fast/events/resources/body-overflow-iframe.html

<!DOCTYPE html>
<style>
html, body {
    height: 100px;
    width: 100px;
    background: green;
    padding: 0;
    margin: 0;
}

div#child {
    position: relative;
    top : 700px;
    width: 50px;
    height: 300px;
    background: red;
}

</style>
<body>
    <div id='child'></div>
</body>

<script>
document.addEventListener("contextmenu", function(){
  top.debug("PASS context_menu_triggered in iframe");
});

document.addEventListener("click", function(){
  top.debug("PASS click_triggered in iframe");
});

window.onload = function(evt) {
  document.scrollingElement.scrollTop = "1000";
  top.debug("iframe's scroll top is " + document.scrollingElement.scrollTop);
  top.postMessage("subframe-loaded", "*");
}

</script>