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chromium/third_party/blink/web_tests/external/wpt/html/browsers/browsing-the-web/unloading-documents/navigation-within-beforeunload-1.html 

<!doctype html>
004-1
<script>
addEventListener("beforeunload",
function() {
if (top.counter++ < 999) {
  location = "navigation-within-beforeunload-2.html?" + top.counter;
}
}, false);
</script>