Report a fatal error on attempt to rename an element declared in SDK.

pkg/analysis_server/lib/src/services/refactoring/rename_class_member.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library services.src.refactoring.rename_class_member;
 
 import 'dart:async';
 
 import 'package:analysis_server/src/protocol_server.dart'
     hide Element, ElementKind;
@@ skipping 40 matching lines @@
   }
 
   @override
   Future<RefactoringStatus> checkFinalConditions() {
     _validator =
         new _ClassMemberValidator.forRename(searchEngine, element, newName);
     return _validator.validate();
   }
 
   @override
-  Future<RefactoringStatus> checkInitialConditions() {
-    RefactoringStatus result = new RefactoringStatus();
+  Future<RefactoringStatus> checkInitialConditions() async {
+    RefactoringStatus result = await super.checkInitialConditions();
     if (element is MethodElement && (element as MethodElement).isOperator) {
       result.addFatalError('Cannot rename operator.');
     }
     return new Future.value(result);
   }
 
   @override
   RefactoringStatus checkNewName() {
     RefactoringStatus result = super.checkNewName();
     if (element is FieldElement) {
@@ skipping 186 matching lines @@
       Element refElement = reference.element;
       LibraryElement refLibrary = refElement.library;
       if (refLibrary != library) {
         String message = format("Renamed {0} will be invisible in '{1}'.",
             getElementKindName(element), getElementQualifiedName(refLibrary));
         result.addError(message, newLocation_fromMatch(reference));
       }
     }
   }
 }