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

tests/compiler/dart2js_native/native_window2_frog_test.dart

Index: tests/compiler/dart2js_native/native_window2_frog_test.dart
diff --git a/tests/compiler/dart2js_native/native_window2_frog_test.dart b/tests/compiler/dart2js_native/native_window2_frog_test.dart
index c1cecefb1612f98b8ce97df777c0d94da246eff1..c252e46224a3759debd83f3eb0f65276daa3f1ed 100644
--- a/tests/compiler/dart2js_native/native_window2_frog_test.dart
+++ b/tests/compiler/dart2js_native/native_window2_frog_test.dart
@@ -2,6 +2,7 @@
 // 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";
 
 abstract class Window {
@@ -10,7 +11,8 @@ abstract class Window {
 
 // Defining this global object makes Frog eager on optimizing
 // call sites where the receiver is typed 'Window'.
-class _DOMWindowJs implements Window native "@*DOMWindow" {
+@Native("@*DOMWindow")
+class _DOMWindowJs implements Window {
   final int document;
 }