function _restoreOverriddenDefault(name, state) {
        if (state.overridden[name]) {
            var language = getLanguage(state.overridden[name]);
            language[state.add](name);
            delete state.overridden[name];
        }
    }
@private

If a default file extension or name was overridden by a pref, restore it.

@param {string} name Extension or filename that should be restored
@param {{overridden: string, add: string}} prefState object for the pref that is currently being updated