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chromium/third_party/blink/web_tests/external/wpt/html/browsers/history/the-history-interface/resources/traverse-during-beforeunload.html 

<!DOCTYPE html>
<meta charset="utf-8">

<script>
"use strict";

window.addEventListener("beforeunload", () => {
  history.back();
});

location.href = "message-opener.sub.html?id=destination";
</script>