Add native_testing library to mock @Native classes

tests/compiler/dart2js_native/native_null_frog_test.dart

Index: tests/compiler/dart2js_native/native_null_frog_test.dart
diff --git a/tests/compiler/dart2js_native/native_null_frog_test.dart b/tests/compiler/dart2js_native/native_null_frog_test.dart
index d554a52a7b172f748c5103e43286df105d929eb0..9bd08eb0721cddf0e0bc1ad510d7ae9b55082990 100644
--- a/tests/compiler/dart2js_native/native_null_frog_test.dart
+++ b/tests/compiler/dart2js_native/native_null_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 for values of some basic types.
 
@@ -24,10 +23,11 @@ A.prototype.returnUndefined = function() { return void 0; };
 A.prototype.returnEmptyString = function() { return ""; };
 A.prototype.returnZero = function() { return 0; };
 makeA = function(){return new A;};
+self.nativeConstructor(A);
 """;
 
-main() {
-  setup();
+@NoInline()
+staticTests() {
   A a = makeA();
   Expect.equals(null, a.returnNull());
   Expect.equals(null, a.returnUndefined());
@@ -39,3 +39,24 @@ main() {
   Expect.isTrue(a.returnZero() is int);
   Expect.equals(0, a.returnZero());
 }
+
+@NoInline()
+dynamicTests() {
+  A a = makeA();
+  Expect.equals(null, confuse(a).returnNull());
+  Expect.equals(null, confuse(a).returnUndefined());
+
+  Expect.equals('', confuse(a).returnEmptyString());
+  Expect.isTrue(confuse(a).returnEmptyString().isEmpty);
+  Expect.isTrue(confuse(a).returnEmptyString() is String);
+
+  Expect.isTrue(confuse(a).returnZero() is int);
+  Expect.equals(0, confuse(a).returnZero());
+}
+
+main() {
+  nativeTesting();
+  setup();
+  staticTests();
+  dynamicTests();
+}