function mkdir(path, mode, callback) {
        if (typeof mode === "function") {
            callback = mode;
            mode = parseInt("0755", 8);
        }
        appshell.fs.makedir(path, mode, function (err) {
            if (err) {
                callback(_mapError(err));
            } else {
                stat(path, function (err, stat) {
                    callback(err, stat);
                });
            }
        });
    }
Create a directory at the given path, and call back asynchronously with
either a FileSystemError string or a stats object for the newly created
directory. The octal mode parameter is optional; if unspecified, the mode
of the created directory is implementation dependent.

@param {string} path
@param {number=} mode The base-eight mode of the newly created directory.
@param {function(?string, FileSystemStats=)=} callback