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

tests/compiler/dart2js_native/subclassing_3_test.dart

Index: tests/compiler/dart2js_native/subclassing_3_test.dart
diff --git a/tests/compiler/dart2js_native/subclassing_3_test.dart b/tests/compiler/dart2js_native/subclassing_3_test.dart
index d73f0c82d0de09626ce85484fccfaddd7ae39013..70595cb996d9f3cba6cd58cc075ac7810c646da9 100644
--- a/tests/compiler/dart2js_native/subclassing_3_test.dart
+++ b/tests/compiler/dart2js_native/subclassing_3_test.dart
@@ -3,7 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 
 import "package:expect/expect.dart";
-import 'dart:_js_helper' show Creates, setNativeSubclassDispatchRecord;
+import 'dart:_js_helper' show Native, Creates, setNativeSubclassDispatchRecord;
 import 'dart:_interceptors' show Interceptor, findInterceptorForType;
 
 // Test calling convention of methods introduced on subclasses of native
@@ -15,7 +15,8 @@ class M {
   miz() => 'M';
 }
 
-class N native "N" {
+@Native("N")
+class N {
   foo(x) => (doFoo)(this, x);
 }