support class native clause

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

Index: pkg/front_end/lib/src/fasta/source/diet_listener.dart
diff --git a/pkg/front_end/lib/src/fasta/source/diet_listener.dart b/pkg/front_end/lib/src/fasta/source/diet_listener.dart
index 77470dfde3346f3c1540e6bd7cad481a473889ed..e67072463161d3ba099a005f3b43146d048afa9b 100644
--- a/pkg/front_end/lib/src/fasta/source/diet_listener.dart
+++ b/pkg/front_end/lib/src/fasta/source/diet_listener.dart
@@ -499,6 +499,11 @@ class DietListener extends StackListener {
     memberScope = library.scope;
   }
 
+  @override
+  void handleNativeClause(Token nativeToken, bool hasName) {
+    debugEvent("NativeClause");
+  }
+
   @override
   void endClassDeclaration(
       int interfacesCount,
@@ -506,6 +511,7 @@ class DietListener extends StackListener {
       Token classKeyword,
       Token extendsKeyword,
       Token implementsKeyword,
+      Token nativeToken,
       Token endToken) {
     debugEvent("ClassDeclaration");
     checkEmpty(beginToken.charOffset);