Revert "Add native_testing library to mock @Native classes"

tests/compiler/dart2js_native/native_class_inheritance2_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 "native_testing.dart";
+import "dart:_js_helper";
+import "package:expect/expect.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 = 100]) native ;
 }
@@ skipping 35 matching lines @@
 function D(){}
 inherits(D, C);
 
 A.prototype.foo = function(a){return 'A.foo(' + a + ')';}
 C.prototype.foo = function(z){return 'C.foo(' + z + ')';}
 
 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(100)', b.foo());
   Expect.equals('C.foo(300)', d.foo());
   // If the above line fails with C.foo(100) then the dispatch to fill in the
   // default got the wrong one, followed by a second dispatch that resolved to
   // the correct native method.
 
   Expect.equals('A.foo(1)', a.foo(1));
   Expect.equals('A.foo(2)', b.foo(2));
   Expect.equals('C.foo(3)', c.foo(3));
   Expect.equals('C.foo(4)', d.foo(4));
 }