Add native_testing library to mock @Native classes

tests/compiler/dart2js_native/native_null_frog_test.dart

 // Copyright (c) 2011, 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.
 
-import "dart:_js_helper";
-import "package:expect/expect.dart";
+import "native_testing.dart";
 
 // Test for values of some basic types.
 
 @Native("A")
 class A {
   returnNull() native ;
   returnUndefined() native ;
   returnEmptyString() native ;
   returnZero() native ;
 }
 
 A makeA() native ;
 
 void setup() native """
 function A() {}
 A.prototype.returnNull = function() { return null; };
 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());
 
   Expect.equals('', a.returnEmptyString());
   Expect.isTrue(a.returnEmptyString().isEmpty);
   Expect.isTrue(a.returnEmptyString() is String);
 
   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();
+}