var nastyGlobalVariable='';
[].forEach.call(
  document.querySelectorAll("tr.zA"),
  function(tr) {
    var tit = tr.querySelector(".xW span").getAttribute("title").replace(/at\s+\d+:\d+.*/, '');
    if (tit != nastyGlobalVariable) {
      nastyGlobalVariable = tit;
      tr.insertAdjacentHTML('beforebegin',
        '<tr class=""><td style="width:2px;background:#ccc"></td><td colspan=7 align=center style="background:#ccc;font-size:12px;padding:2px">'
        + tit + '</td></tr>')
    }
  }
);