code: function(cb) {
      // If we're inside phonegap use its event.
      if (window.phonegap) {
        return document.addEventListener("offline", cb, false);
      } else if (window.addEventListener) {
        // With the offline HTML5 event from the window
        this.addLocalEventListener(window, "offline", cb);
      } else {
        /*
        Works in IE with the Work Offline option in the 
        File menu and pulling the ethernet cable
        Ref: http://robertnyman.com/html5/offline/online-offline-events.html
      */
        document.body.onoffline = cb;
      }
    }
docs: Calls cb when the app is offline from the backend
  
  TODO: Find a kludge for this, for Firefox. Firefox only triggers offline when
  the user sets the browser to "Offline mode"
  
  @param {Function} cb.