URL : <span id="url"></span><br>
sessionStorage.name : <span id="name"></span>

<form name=loopback action="" method=GET>
<input name=page value=last></input>
</form>

<script>
  // Regression test for https://crbug.com/1311546.
  // This test consists of following 3 pages in its history.
  //   a. back-forward.html
  //   b. go-forwards-then-back.html
  //   c. go-forwards-then-back.html?page=last
  // It expects to navigate a.->b.->c.-(back)->b. and test-runner
  // dumps the HTML of b.
  window.addEventListener('pageshow', (e) => {
    document.getElementById("url").innerText = document.URL;
    sessionStorage.setItem("name", parseInt(sessionStorage.getItem("name")) + 1);
    document.getElementById("name").innerText = sessionStorage.getItem("name");

    setTimeout(function() {
      const name = sessionStorage.getItem("name");
      if (name == 1) {
        // Showing b. for the first time.
        // Navigate foward to c.
        document.loopback.submit();
      } else if (name == 2) {
        // Showing c.
        // Go back to b.
        history.back();
      } else {
        // Showing b. for the second time, should dump b.
        if (window.testRunner)
          testRunner.notifyDone();
      }
    }, 0);
  });
</script>