anchor.diff:  
     List<File> _dartFiles(List<FileSystemEntity> entities) {
       return new List<File>.from(entities
  -      .where((FileSystemEntity entity) => entity is File)
  -      .where((File file) => file.path.endsWith('.dart')));
  +      .where((FileSystemEntity entity) => entity is File && entity.path.endsWith('.dart')));
     }
   
     void _printHelp() {
  
positive.code:   final Observatory observatory;
  
    String fsName;
    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));
    }
  
    /// Flush any modified files to the devfs.
    Future<Null> flush() async {
      List<DevFSFileEntry> toSend = entries.values
        .where((DevFSFileEntry entry) => entry.isModified)
        .toList();
  
      for (DevFSFileEntry entry in toSend) {
        printTrace('sending devfs://$fsName/${entry.devPath}');
        entry.updateLastModified();
      }
  
negative.code:     _sendFiles(directory, '', _dartFiles(directory.listSync()));
  
      directory = new Directory('lib');
      _sendFiles(directory, 'lib', _dartFiles(directory.listSync(recursive: true)));
  
      // Send the packages.
      if (FileSystemEntity.isFileSync(kPackagesFileName)) {
  