function _fileComparator(a, b) {
            var aIsCSS = LanguageManager.getLanguageForPath(a.fullPath).getId() === "css",
                bIsCSS = LanguageManager.getLanguageForPath(b.fullPath).getId() === "css";
            if (aIsCSS && !bIsCSS) {
                return 1;
            } else if (!aIsCSS && bIsCSS) {
                return -1;
            } else {
                return FileUtils.comparePaths(a.fullPath, b.fullPath);
            }
        }
@private
Sort files with LESS/SCSS above CSS, and then within each grouping sort by path & filename
(the same order we use for Find in Files)
@param {!File} a, b
@return {number}