Add @Native(...) annotation for native class names.

tests/compiler/dart2js_native/subclassing_super_field_2_test.dart

 // Copyright (c) 2013, 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:expect/expect.dart";
 import 'dart:_foreign_helper' show JS;
-import 'dart:_js_helper' show Creates, setNativeSubclassDispatchRecord;
+import 'dart:_js_helper' show Native, Creates, setNativeSubclassDispatchRecord;
 import 'dart:_interceptors' show
     findInterceptorForType, findConstructorForNativeSubclassType;
 
 // Test for fields with same name as native fields.  We expect N.foo to have the
 // property name 'foo' and A.foo and B.foo to have non-conflicting names.
 
-class N native "N" {
+@Native("N")
+class N {
   var foo;
   N.init();
 }
 
 class A extends N {
   var foo = 222;
   A.init() : super.init();
   Nfoo() => super.foo;     // TODO(sra): Fix compiler assert.
 }
 
@@ skipping 35 matching lines @@
   print(b);
 
   Expect.equals(333, inscrutable(b).Bfoo());
   Expect.equals(222, inscrutable(b).Afoo());
   Expect.equals(111, inscrutable(b).Nfoo());
 
   Expect.equals(333, b.Bfoo());
   Expect.equals(222, b.Afoo());
   Expect.equals(111, b.Nfoo());
 }