anchor.diff:    final Observatory observatory;
   
     String fsName;
  -  Map<String, DevFSFileEntry> entries = <String, DevFSFileEntry>{};
  +  Map<String, _DevFSFileEntry> entries = <String, _DevFSFileEntry>{};
   
     Future<dynamic> init() => observatory.createDevFS(fsName);
   
     void stageFile(String devPath, File file) {
  -    entries.putIfAbsent(devPath, () => new DevFSFileEntry(devPath, file));
  +    entries.putIfAbsent(devPath, () => new _DevFSFileEntry(devPath, file));
     }
   
     /// Flush any modified files to the devfs.
     Future<Null> flush() async {
  -    List<DevFSFileEntry> toSend = entries.values
  -      .where((DevFSFileEntry entry) => entry.isModified)
  +    List<_DevFSFileEntry> toSend = entries.values
  +      .where((_DevFSFileEntry entry) => entry.isModified)
         .toList();
   
  -    for (DevFSFileEntry entry in toSend) {
  +    for (_DevFSFileEntry entry in toSend) {
         printTrace('sending devfs://$fsName/${entry.devPath}');
         entry.updateLastModified();
       }
  
positive.code:     try {
        await devFS.flush();
      } catch (error) {
        printError('Error sending DevFS files: $error');
      }
    }
  
  
negative.code: 
    List<File> _dartFiles(List<FileSystemEntity> entities) {
      return new List<File>.from(entities
        .where((FileSystemEntity entity) => entity is File && entity.path.endsWith('.dart')));
    }
  
    void _printHelp() {
  