chromium/third_party/blink/web_tests/http/tests/navigation/resources/top-go-back.html

Target of redirect after POST request.
<script>
      onload = function() {
          if (!sessionStorage.didNav) {
            sessionStorage.didNav = true;
            setTimeout(function() {top.location.href = 'go-back.html'}, 0);
          }
      };
</script>