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

tests/compiler/dart2js_native/fixup_get_tag_test.dart

Index: tests/compiler/dart2js_native/fixup_get_tag_test.dart
diff --git a/tests/compiler/dart2js_native/fixup_get_tag_test.dart b/tests/compiler/dart2js_native/fixup_get_tag_test.dart
index 957fd2574d2176e6c5a1b89abac610d576e0302b..0f689867e4a40edb67952f3e5e316284117bac49 100644
--- a/tests/compiler/dart2js_native/fixup_get_tag_test.dart
+++ b/tests/compiler/dart2js_native/fixup_get_tag_test.dart
@@ -2,11 +2,13 @@
 // 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";
 
 // Test for dartExperimentalFixupGetTag.
 
-class Foo native "A" { // There is one native class with dispatch tag 'A'.
+@Native("A")
+class Foo { // There is one native class with dispatch tag 'A'.
   token() native;
 }