Add native_testing library to mock @Native classes

tests/compiler/dart2js_native/native_method_rename2_frog_test.dart

Index: tests/compiler/dart2js_native/native_method_rename2_frog_test.dart
diff --git a/tests/compiler/dart2js_native/native_method_rename2_frog_test.dart b/tests/compiler/dart2js_native/native_method_rename2_frog_test.dart
index e375f2ff0d791d8b014d7f48b8d6d134d0abdb62..5979e1e5ff808151a1ae7b28c3ed7b02944efad9 100644
--- a/tests/compiler/dart2js_native/native_method_rename2_frog_test.dart
+++ b/tests/compiler/dart2js_native/native_method_rename2_frog_test.dart
@@ -4,8 +4,7 @@
 
 // Test the feature where the native string declares the native method's name.
 
-import "package:expect/expect.dart";
-import 'dart:_js_helper' show Native, JSName;
+import "native_testing.dart";
 
 @Native("A")
 class A {
@@ -42,6 +41,9 @@ B.prototype.fooB = function(){return 200;};
 
 makeA = function(){return new A};
 makeB = function(){return new B};
+
+self.nativeConstructor(A);
+self.nativeConstructor(B);
 """;
 
 testDynamic() {
@@ -76,6 +78,7 @@ testTyped() {
 }
 
 main() {
+  nativeTesting();
   setup();
 
   testDynamic();