code: function (evt) {
                  var state = ariaUtilsJson.copy(evt.state), title;
                  if (state && state.__info) {
                      title = state.__info.title;
                      delete state.__info;
                  } else {
                      var stateInfo = this._retrieveFromMemory();
                      title = stateInfo ? stateInfo.state.title : null;
                  }
                  this.state = state;
                  if (title) {
                      this._setTitle(title);
                  }
                  this.$raiseEvent({
                      name : "popstate",
                      state : state
                  });
              }
docs: Methods that are specific to browsers that support HTML5 history API. 
  React to native onpopstate event by setting the title and raising the onpopstate class event. Only used
  in browsers that support HTML5 history API.
  @param {Object} Event object
  @private