support class native clause

pkg/analyzer/tool/summary/mini_ast.dart

 // Copyright (c) 2017, 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.
 
 import 'package:front_end/src/fasta/problems.dart'
     show internalProblem, unsupported;
 import 'package:front_end/src/fasta/messages.dart' show Message;
 import 'package:front_end/src/fasta/parser.dart';
 import 'package:front_end/src/fasta/source/stack_listener.dart';
 import 'package:front_end/src/scanner/token.dart';
@@ skipping 175 matching lines @@
     debugEvent("ClassBody");
     push(popList(memberCount));
   }
 
   void endClassDeclaration(
       int interfacesCount,
       Token beginToken,
       Token classKeyword,
       Token extendsKeyword,
       Token implementsKeyword,
+      Token nativeToken,
       Token endToken) {
     debugEvent("ClassDeclaration");
     List<ClassMember> members = pop();
+    if (nativeToken?.next?.type == TokenType.STRING) {
+      pop(); // native clause - StringLiteral
+    }
     TypeName superclass = pop();
     pop(); // Type variables
     String name = pop();
     List<Annotation> metadata = pop();
     Comment comment = pop();
     compilationUnit.declarations.add(
         new ClassDeclaration(comment, metadata, name, superclass, members));
   }
 
   @override
@@ skipping 267 matching lines @@
   final String name;
 
   final List<TypeName> typeArguments;
 
   TypeName(this.name, this.typeArguments);
 }
 
 /// "Mini AST" representation of an expression which summary code generation
 /// need not be concerned about.
 class UnknownExpression extends Expression {}