code: function _purgeAllExceptWorkingSet() {
              _mrofList = _createMROFList();
              $mrofList.empty();
              _createMROFDisplayList(true);
              $currentContext = null;
              PreferencesManager.setViewState(OPEN_FILES_VIEW_STATE, _mrofList, _getPrefsContext(), true);
          }
docs: Clears the MROF list in memory and pop over but retains the working set entries
  @private