Add native_testing library to mock @Native classes

tests/compiler/dart2js_native/super_call_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 to see if resolving a hidden native class's method interferes with
 // subsequent resolving the subclass's method.  This might happen if the
 // superclass caches the method in the prototype, so shadowing the dispatcher
 // stored on Object.prototype.
 
 @Native("A")
 class A {
   foo() => 'A.foo ${bar()}';
   bar() => 'A.bar';
@@ skipping 38 matching lines @@
 inherits(B, A);
 function C(){}
 inherits(C, B);
 function D(){}
 inherits(D, C);
 
 makeA = function(){return new A};
 makeB = function(){return new B};
 makeC = function(){return new C};
 makeD = function(){return new D};
+
+self.nativeConstructor(A);
+self.nativeConstructor(B);
+self.nativeConstructor(C);
+self.nativeConstructor(D);
 """;
 
 main() {
+  nativeTesting();
   setup();
 
   var a = makeA();
   var b = makeB();
   var c = makeC();
   var d = makeD();
 
   Expect.equals('A.foo A.bar', a.foo());
   Expect.equals('A.foo B.bar', b.foo());
   Expect.equals('C.foo; super.foo = A.foo C.bar', c.foo());
   Expect.equals('C.foo; super.foo = A.foo D.bar', d.foo());
 }