Revert "Add native_testing library to mock @Native classes"

tests/compiler/dart2js_native/native_call_arity2_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";
 
 // This is a similar test to NativeCallArity1FrogTest, but makes sure
 // that subclasses also get the right number of arguments.
 
 @Native("A")
 class A {
   int foo([x, y]) native ;
 }
 
 @Native("B")
@@ skipping 17 matching lines @@
 }
 function A() {}
 A.prototype.foo = function () { return arguments.length; };
 
 function B() {}
 B.prototype.foo = function () { return arguments.length; };
 inherits(B, A);
 
 makeA = function(){return new A;};
 makeB = function(){return new B;};
-
-self.nativeConstructor(A);
-self.nativeConstructor(B);
 """;
 
 testDynamicContext() {
-  var a = confuse(makeA());
-  var b = confuse(makeB());
+  var things = [makeA(), makeB()];
+  var a = things[0];
+  var b = things[1];
 
   Expect.equals(0, a.foo());
   Expect.equals(1, a.foo(10));
   Expect.equals(2, a.foo(10, 20));
   Expect.throws(() => a.foo(10, 20, 30));
 
   Expect.equals(1, a.foo(10));
   Expect.equals(2, a.foo(null, 20));
   Expect.throws(() => a.foo(10, 20, 30));
 
@@ skipping 24 matching lines @@
   Expect.equals(1, b.foo(10));
   Expect.equals(2, b.foo(10, 20));
   Expect.throws(() => b.foo(10, 20, 30));
 
   Expect.equals(1, b.foo(10));
   Expect.equals(2, b.foo(null, 20));
   Expect.throws(() => b.foo(10, 20, 30));
 }
 
 main() {
-  nativeTesting();
   setup();
   testDynamicContext();
   testStaticContext();
 }