anchor.diff:  import '../../descriptor.dart';
   import '../../scheduled_test.dart';
   import '../utils.dart';
  -
  -/// A path builder to ensure that [load] uses POSIX paths.
  -final path.Builder _path = new path.Builder(style: path.Style.posix);
   
   /// A descriptor describing a directory containing multiple files.
   class DirectoryDescriptor extends Descriptor implements LoadableDescriptor {
  
positive.code:           return (matchingEntries.first as ReadableDescriptor).read();
          } else {
            return (matchingEntries.first as LoadableDescriptor)
                .load(_path.joinAll(remainingPath));
          }
        }
      }));
  
negative.code: 
    Stream<List<int>> load(String pathToLoad) {
      return futureStream(new Future.value().then((_) {
        if (path.posix.isAbsolute(pathToLoad)) {
          throw new ArgumentError("Can't load absolute path '$pathToLoad'.");
        }
  
        var split = path.posix.split(path.posix.normalize(pathToLoad));
        if (split.isEmpty || split.first == '.' || split.first == '..') {
          throw new ArgumentError("Can't load '$pathToLoad' from within "
              "'$name'.");
  