getInitialViewFilePath = function () {
            return (self._viewList.length > 0) ? self._viewList[0].fullPath : null;
        }
serializes the pane state from JSON
@param {!Object} state - the state to load
@return {jQuery.Promise} A promise which resolves to
             {fullPath:string, paneId:string}
             which can be passed as command data to FILE_OPEN