do not allow built-in keywords to specified when refactoring

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

Index: pkg/analysis_server/lib/src/services/refactoring/naming_conventions.dart
diff --git a/pkg/analysis_server/lib/src/services/refactoring/naming_conventions.dart b/pkg/analysis_server/lib/src/services/refactoring/naming_conventions.dart
index 892da77aa6129a674138e21aaa2d51e0ba17d3cc..7b5dab2fb1e1f17c7f40c9e195736f8d538b6265 100644
--- a/pkg/analysis_server/lib/src/services/refactoring/naming_conventions.dart
+++ b/pkg/analysis_server/lib/src/services/refactoring/naming_conventions.dart
@@ -6,7 +6,7 @@ library services.src.refactoring.naming_conventions;
 
 import 'package:analysis_server/src/services/correction/status.dart';
 import 'package:analysis_server/src/services/correction/strings.dart';
-import 'package:analyzer/dart/ast/token.dart';
+import 'package:front_end/src/fasta/scanner/keyword.dart' as fasta;
 
 /**
  * Returns the [RefactoringStatus] with severity:
@@ -167,8 +167,8 @@ RefactoringStatus _validateIdentifier(
   }
   // keyword
   {
-    Keyword keyword = Keyword.keywords[identifier];
-    if (keyword != null && !keyword.isPseudoKeyword) {
+    fasta.Keyword keyword = fasta.Keyword.keywords[identifier];
+    if (keyword != null) {
       String message = "$desc must not be a keyword.";
       return new RefactoringStatus.fatal(message);
     }