anchor.diff:    }
   
     String toString() => 'InstanceMirror on ${Error.safeToString(reflectee)}';
  +
  +  // TODO(ahe): Remove this method from the API.
  +  MirrorSystem get mirrors => currentJsMirrorSystem;
   }
   
   class JsClassMirror extends JsTypeMirror with JsObjectMirror
  
positive.code:     }
      return _superclass == this ? null : _superclass;
    }
  }
  
  class JsVariableMirror extends JsDeclarationMirror implements VariableMirror {
  
negative.code:   bool get isTopLevel => owner != null && owner is LibraryMirror;
  
    String toString() => "$_prettyName on '${n(simpleName)}'";
  
    // TODO(ahe): Implement this.
    SourceLocation get location => throw new UnimplementedError();
  }
  
  class JsTypeMirror extends JsDeclarationMirror implements TypeMirror {
  