code: function doReadFile(stat) {
              if (stat.size > (FileUtils.MAX_FILE_SIZE)) {
                  callback(FileSystemError.EXCEEDS_MAX_FILE_SIZE);
              } else {
                  appshell.fs.readFile(path, encoding, function (_err, _data, encoding, preserveBOM) {
                      if (_err) {
                          callback(_mapError(_err));
                      } else {
                          callback(null, _data, encoding, preserveBOM, stat);
                      }
                  });
              }
          }
docs: callback to be executed when the call to stat completes or immediately if a stat object was passed as an argument