support class native clause

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

Index: pkg/front_end/lib/src/fasta/source/outline_builder.dart
diff --git a/pkg/front_end/lib/src/fasta/source/outline_builder.dart b/pkg/front_end/lib/src/fasta/source/outline_builder.dart
index 680c6022738c84db845bf54dcc38de1898d5c5f3..a0a234256e5c5c164b93008addd72e77f696c285 100644
--- a/pkg/front_end/lib/src/fasta/source/outline_builder.dart
+++ b/pkg/front_end/lib/src/fasta/source/outline_builder.dart
@@ -292,6 +292,15 @@ class OutlineBuilder extends UnhandledListener {
     library.currentDeclaration.name = name.lexeme;
   }
 
+  @override
+  void handleNativeClause(Token nativeToken, bool hasName) {
+    if (hasName) {
+      // Pop the native clause which in this case is a StringLiteral.
+      pop(); // Char offset.
+      pop(); // String.
+    }
+  }
+
   @override
   void endClassDeclaration(
       int interfacesCount,
@@ -299,6 +308,7 @@ class OutlineBuilder extends UnhandledListener {
       Token classKeyword,
       Token extendsKeyword,
       Token implementsKeyword,
+      Token nativeToken,
       Token endToken) {
     debugEvent("endClassDeclaration");
     String documentationComment = _getDocumentationComment(beginToken);