<!DOCTYPE html>
<meta charset="utf-8">
<title>Traversing the history during unload</title>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>

<body>
<script>
"use strict";

async_test(t => {
  const w = window.open("resources/message-opener.sub.html?id=start");
  t.add_cleanup(() => w.close());

  const messages = [];
  window.addEventListener("message", t.step_func(({ data }) => {
    messages.push(data);

    if (messages.length === 1) {
      assert