support class native clause

pkg/front_end/lib/src/fasta/source/directive_listener.dart

Index: pkg/front_end/lib/src/fasta/source/directive_listener.dart
diff --git a/pkg/front_end/lib/src/fasta/source/directive_listener.dart b/pkg/front_end/lib/src/fasta/source/directive_listener.dart
index dcb47292ee24f1075a2240fafc5912844932ff2a..3fa4baf7fb4c60dcef8fadda38c516c50d56b537 100644
--- a/pkg/front_end/lib/src/fasta/source/directive_listener.dart
+++ b/pkg/front_end/lib/src/fasta/source/directive_listener.dart
@@ -110,12 +110,12 @@ class DirectiveListener extends Listener {
 
   /// Defines how native clauses are handled. By default, they are not handled
   /// and an error is thrown;
-  Token handleNativeClause(Token token) => null;
+  Token handleNativeClauseError(Token token) => null;
 
   @override
   Token handleUnrecoverableError(Token token, Message message) {
     if (message.code == codeExpectedBlockToSkip) {
-      Token recover = handleNativeClause(token);
+      Token recover = handleNativeClauseError(token);
       if (recover != null) return recover;
     }
     return super.handleUnrecoverableError(token, message);