code: function preferencesReload() {
            return this.initializedPromise.then(function () {
              this._readFromStorage(this.defaults).then(function (prefObj) {
                if (prefObj) {
                  this.prefs = prefObj;
                }
              }.bind(this));
            }.bind(this));
          }
docs: Replace the current preference values with the ones from storage.
  @return {Promise} A promise that is resolved when the preference values
  have been updated.