docs: function windowCmp(tabWindowA, tabWindowB) {
    // focused window very first:
    var fA = tabWindowA.focused;
    var fB = tabWindowB.focused;
    if (fA !== fB) {
      if (fA) {
        return -1;
      }
      return 1;
    }
  
    // open windows first:
    if (tabWindowA.open !== tabWindowB.open) {
      if (tabWindowA.open) {
        return -1;
      }
      return 1;
    }
  
    var tA = tabWindowA.title;
    var tB = tabWindowB.title;
    return tA.localeCompare(tB);
  }