anchor.diff:      _dartSdk = new _DirectoryBasedDartSdkProxy(new JavaFile(sdkDir));
       _dartSdk.context.analysisOptions = options;
   
  -    _context.sourceFactory = new SourceFactory.con2([
  +    _context.sourceFactory = new SourceFactory([
           new DartUriResolverProxy(_dartSdk),
           new _AssetUriResolver(this)]);
     }
  
positive.code:   }
  
    /// Contents of the file.
    String get contents => _contents;
  
    /// Logger for the current transform.
    ///
  
negative.code:     return source;
    }
  
    Source fromEncoding(UriKind kind, Uri uri) =>
        throw new UnsupportedError('fromEncoding is not supported');
  
    Uri restoreAbsolute(Source source) =>
  