anchor.diff:    }
   
     String toString() => "ClosureMirror on '${Error.safeToString(reflectee)}'";
  +
  +  // TODO(ahe): Implement these.
  +  String get source => throw new UnimplementedError();
  +  Future<InstanceMirror> findInContext(Symbol name)
  +      => throw new UnimplementedError();
   }
   
   class JsMethodMirror extends JsDeclarationMirror implements MethodMirror {
  
positive.code:     }
      return result;
    }
  }
  
  abstract class JsMirror {
  
negative.code: 
    // TODO(ahe): Doesn't match the specification, see http://dartbug.com/11569.
    bool get isTopLevel => true;
  
    // TODO(ahe): Implement this.
    List<InstanceMirror> get metadata => throw new UnimplementedError();
  }
  
  class JsLibraryMirror extends JsDeclarationMirror with JsObjectMirror
  