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    <meta http-equiv="content-type" content="text/html; charset=utf-8">
    <title>Bug 1300461</title>
  </head>
  <!-- The empty unload handler is to prevent bfcache. -->
  <body onload="test();" onunload="">
    <script>
      let Ci = SpecialPowers.Ci;
      let webNav = SpecialPowers.wrap(window)
                                .docShell
                                .QueryInterface(Ci.nsIWebNavigation);
      let shistory = webNav.sessionHistory;
      async function test() {
        if (opener) {
          opener.info("file_bug1300461_back.html");
          opener.is(shistory.count, 2, "check history length");
          opener.is(shistory.index, 1, "check history index");
          if (!SpecialPowers.Services.appinfo.sessionHistoryInParent) {
            opener.is(shistory.legacySHistory.requestedIndex, -1, "check requestedIndex");
          } else {
            let index = await opener.getSHRequestedIndex(SpecialPowers.wrap(window).browsingContext.id);
            opener.is(index, -1, "check requestedIndex");
          }

          opener.ok(webNav.canGoBack, "check canGoBack");
          if (opener.testCount == 1) {
            opener.info("replaceState to redirect.html");
            window.history.replaceState({}, "", "file_bug1300461_redirect.html");
          }
          window.history.back();
        }
      }
    </script>
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