slow-message-source-with-history-and-location.html

<!DOCTYPE html>
<meta charset="utf-8">
<title>Subframe or popup</title>

<script>
"use strict";
(window.opener || window.parent).postMessage(
  { historyLength: history.length, locationHref: location.href },
  "*"
);
</script>

<!--
  This delays the load event, hopefully long enough that we can do whatever before-load action we're aiming for.
-->
<img src="/common/slow.py">

chromium/third_party/blink/web_tests/external/wpt/html/browsers/browsing-the-web/navigating-across-documents/replace-before-load/resources/slow-message-source-with-history-and-location.html