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

tests/compiler/dart2js_native/native_mirror_test.dart

Index: tests/compiler/dart2js_native/native_mirror_test.dart
diff --git a/tests/compiler/dart2js_native/native_mirror_test.dart b/tests/compiler/dart2js_native/native_mirror_test.dart
index 79b842c1003b9ce6a3c295b6ecb7f9260702583e..58e8ffed0fa76a9a68a5a982b120c0ff2759255d 100644
--- a/tests/compiler/dart2js_native/native_mirror_test.dart
+++ b/tests/compiler/dart2js_native/native_mirror_test.dart
@@ -10,9 +10,11 @@
 // convention for others, making this fail.
 
 import "package:expect/expect.dart";
+import "dart:_js_helper";
 import "dart:mirrors";
 
-class A native "A" {
+@Native("A")
+class A {
   final foo;
 }