Revert "Add native_testing library to mock @Native classes"

tests/compiler/dart2js_native/native_equals_frog_test.dart

 // Copyright (c) 2013, 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";
 
 @Native("A")
 class A {}
 
-int calls = 0;
-@Native("B")
-class B {
-  bool operator==(other) {
-    ++calls;
-    return other is B;
-  }
-  int get hashCode => 1;
-}
-
 makeA() native ;
-makeB() native ;
 
 void setup() native """
 function A() {}
-function B() {}
 makeA = function(){return new A;};
-makeB = function(){return new B;};
-
-self.nativeConstructor(B);
 """;
 
 main() {
-  nativeTesting();
   setup();
   var a = makeA();
   Expect.isTrue(a == a);
   Expect.isTrue(identical(a, a));
 
   Expect.isFalse(a == makeA());
   Expect.isFalse(identical(a, makeA()));
-
-  var b = makeB();
-  Expect.isTrue(b == b);
-  Expect.isTrue(identical(b, b));
-
-  Expect.isTrue(b == makeB());
-  Expect.isFalse(identical(b, makeB()));
-
-  Expect.equals(2, calls);
 }