Add native_testing library to mock @Native classes

tests/compiler/dart2js_native/native_class_avoids_hidden_name_frog_test.dart

Index: tests/compiler/dart2js_native/native_class_avoids_hidden_name_frog_test.dart
diff --git a/tests/compiler/dart2js_native/native_class_avoids_hidden_name_frog_test.dart b/tests/compiler/dart2js_native/native_class_avoids_hidden_name_frog_test.dart
index 8690e4b856605d04c7a158b4e22c72d49e67fdd0..3f286822d7304c01f0696579be69a63ffa78bfee 100644
--- a/tests/compiler/dart2js_native/native_class_avoids_hidden_name_frog_test.dart
+++ b/tests/compiler/dart2js_native/native_class_avoids_hidden_name_frog_test.dart
@@ -2,8 +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";
+import "native_testing.dart";
 
 // Test that hidden native class names are not used by generated code.
 
@@ -41,18 +40,18 @@ function BB(){}
 function CC(){}
 makeA = function(){return new BB};  // AA is native "BB"
 makeB = function(){return new CC};  // BB is native "CC"
+self.nativeConstructor(BB);
+self.nativeConstructor(CC);
 """;
 
-int inscrutable(int x) => x == 0 ? 0 : x | inscrutable(x & (x - 1));
-
 main() {
+  nativeTesting();
   setup1();
   setup2();
 
-  var things = [AA.create(), BB.create(), CC.create()];
-  var a = things[inscrutable(0)];
-  var b = things[inscrutable(1)];
-  var c = things[inscrutable(2)];
+  var a = confuse(AA.create());
+  var b = confuse(BB.create());
+  var c = confuse(CC.create());
 
   Expect.equals('AA', a.name);
   Expect.equals('BB', b.name);