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

tests/compiler/dart2js_native/is_check_test.dart

Index: tests/compiler/dart2js_native/is_check_test.dart
diff --git a/tests/compiler/dart2js_native/is_check_test.dart b/tests/compiler/dart2js_native/is_check_test.dart
index db045025b43c3a74fcc4bfe3f987650a3a66db7e..ecc42b2223019aede243285d5f30f4bacb6c152d 100644
--- a/tests/compiler/dart2js_native/is_check_test.dart
+++ b/tests/compiler/dart2js_native/is_check_test.dart
@@ -2,9 +2,11 @@
 // 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 "dart:_js_helper";
 import "package:expect/expect.dart";
 
-class A native "A" {}
+@Native("A")
+class A {}
 
 main() {
   var a = [new Object()];