Add a test that native classes work with operator==.

tests/compiler/dart2js_native/native_equals_frog_test.dart

Index: tests/compiler/dart2js_native/native_equals_frog_test.dart
===================================================================
--- tests/compiler/dart2js_native/native_equals_frog_test.dart	(revision 17345)
+++ tests/compiler/dart2js_native/native_equals_frog_test.dart	(working copy)
@@ -1,4 +1,4 @@
-// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
+// Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // 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.
 
@@ -13,5 +13,10 @@
 
 main() {
   setup();
-  Expect.isTrue(makeA().toString() is String);
+  var a = makeA();
+  Expect.isTrue(a == a);
+  Expect.isTrue(identical(a, a));
+
+  Expect.isFalse(a == makeA());
+  Expect.isFalse(identical(a, makeA()));
 }