function getNextPrevFile(inc) {
        DeprecationWarning.deprecationWarning("Use MainViewManager.traverseToNextViewByMRU() instead of DocumentManager.getNextPrevFile()", true);
        var result = MainViewManager.traverseToNextViewByMRU(inc);
        if (result) {
            return result.file;
        }
        return null;
    }
Get the next or previous file in the working set, in MRU order (relative to currentDocument). May
return currentDocument itself if working set is length 1.
@deprecated use MainViewManager.traverseToNextViewByMRU() instead