anchor.diff:  
         output.add(generateSourceMapTag(mapUri, partUri));
         output.close();
  -      outputSourceMap(output, lineColumnCollector, hunkPrefix, mapUri, partUri);
  +      outputSourceMap(output, lineColumnCollector, partName, mapUri, partUri);
       } else {
         output.close();
       }
  
positive.code:   static const String deferredInitializersGlobal =
        r"$__dart_deferred_initializers__";
  
    static const String deferredExtension = "part.js";
  
    static const String typeNameProperty = r"builtin$cls";
  
negative.code:       Uri mapUri, partUri;
        Uri sourceMapUri = compiler.sourceMapUri;
        Uri outputUri = compiler.outputUri;
        String partName = "$hunkPrefix.$partExtension";
        String hunkFileName = "$hunkPrefix.$deferredExtension";
  
        if (sourceMapUri != null) {
          String mapFileName = hunkFileName + ".map";
          List<String> mapSegments = sourceMapUri.pathSegments.toList();
          mapSegments[mapSegments.length - 1] = mapFileName;
          mapUri = compiler.sourceMapUri.replace(pathSegments: mapSegments);
        }
  
        if (outputUri != null) {
          List<String> partSegments = outputUri.pathSegments.toList();
          partSegments[partSegments.length - 1] = hunkFileName;
          partUri = compiler.outputUri.replace(pathSegments: partSegments);
  