anchor.diff:  
   /// Analyzes set of libraries by getting a mirror system and triggers the
   /// documentation of the libraries.
  -Future<MirrorSystem> getMirrorSystem(List<Uri> libraries,
  +Future<MirrorSystem> getMirrorSystem(List<String> libraries,
       {String packageRoot, bool parseSdk: false}) {
     if (libraries.isEmpty) throw new StateError('No Libraries.');
     // Finds the root of SDK library based off the location of docgen.
  
positive.code:       var contents = new File(f).readAsStringSync();
        if (!(contents.contains(new RegExp('\npart of ')) ||
            contents.startsWith(new RegExp('part of ')))) {
          libraries.add(new Uri.file(path.normalize(path.absolute(f))));
          logger.info('Added to libraries: $f');
        }
      }
    });
    return libraries;
  }
  
  String _findPackageRoot(String directory) {
  
negative.code:       _coreLibrary = _sdkLibraries.singleWhere((lib) =>
            lib.uri.toString().startsWith('dart:core'));
        var availableLibrariesByPath = new Map.fromIterables(
            availableLibraries.map((each) => each.uri.toFilePath()),
            availableLibraries);
        var librariesToDocument = requestedLibraries.map(
            (each) => availableLibrariesByPath.putIfAbsent(each,
  