anchor.diff:  /**
    * Creates documentation for filtered libraries.
    */
  -void _documentLibraries(List<LibraryMirror> libs,
  -    {bool includeSdk: false, bool outputToYaml: true, bool append: false}) {
  +void _documentLibraries(List<LibraryMirror> libs, {bool includeSdk: false,
  +    bool outputToYaml: true, bool append: false, bool parseSdk: false}) {
     libs.forEach((lib) {
       // Files belonging to the SDK have a uri that begins with 'dart:'.
       if (includeSdk || !lib.uri.toString().startsWith('dart:')) {
  
positive.code:       if (mirrorSystem.libraries.isEmpty) {
          throw new StateError('No library mirrors were created.');
        }
        _documentLibraries(mirrorSystem.libraries.values,
            includeSdk: includeSdk, outputToYaml: outputToYaml, append: append);
  
        return true;
      });
  
negative.code:   // intermediate classes created by mixins are included. 
    entityMap.values.where((e) => e is Class).forEach((c) => c.makeValid());
    // Everything is a subclass of Object, therefore empty the list to avoid a
    // giant list of subclasses to be printed out.
    if (parseSdk) entityMap['dart.core.Object'].subclasses.clear();
    
    var filteredEntities = entityMap.values.where(_isVisible);
    // Output libraries and classes to file after all information is generated.
  