Add native_testing library to mock @Native classes

tests/compiler/dart2js_native/subclassing_super_call_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 "package:expect/expect.dart";
-import 'dart:_foreign_helper' show JS;
-import 'dart:_js_helper' show Native, Creates, setNativeSubclassDispatchRecord;
+import "native_testing.dart";
+import 'dart:_js_helper' show setNativeSubclassDispatchRecord;
 import 'dart:_interceptors'
     show findInterceptorForType, findConstructorForNativeSubclassType;
 
 // Test for super access from classes that extend native classes.
 
 @Native("N1")
 class N1 {}
 
 @Native("N2")
 class N2 extends N1 {
@@ skipping 28 matching lines @@
 void setup() native r"""
 function N2() {}
 N2.prototype.foo = function() { return "foo:" + this.text; }
 function BB() {}
 BB.prototype.__proto__ = N2.prototype;
 makeBB = function(){return new BB;};
 
 getBBPrototype = function(){return BB.prototype;};
 """;
 
-var inscrutable;
-
 testSuperOnNative() {
   BB b1 = makeBB();
   BB b2 = makeBB();
 
   var constructor = findConstructorForNativeSubclassType(BB, 'init');
   Expect.isNotNull(constructor);
   JS('', '#(#)', constructor, b1);
   JS('', '#(#)', constructor, b2);
 
-  b1.text = inscrutable('one');
-  b2.text = inscrutable('two');
+  b1.text = confuse('one');
+  b2.text = confuse('two');
 
-  print('b1.text ${inscrutable(b1).text}');
-  print('b2.text ${inscrutable(b2).text}');
+  print('b1.text ${confuse(b1).text}');
+  print('b2.text ${confuse(b2).text}');
 
-  print('b1.foo() ${inscrutable(b1).foo()}');
-  print('b2.foo() ${inscrutable(b2).foo()}');
+  print('b1.foo() ${confuse(b1).foo()}');
+  print('b2.foo() ${confuse(b2).foo()}');
 
   Expect.equals('one', b1.text);
   Expect.equals('two', b2.text);
 
   Expect.equals('foo:one', b1.foo());
   Expect.equals('foo:two', b2.foo());
 
-  inscrutable(b1).text = inscrutable('three');
-  inscrutable(b2).text = inscrutable('four');
+  confuse(b1).text = confuse('three');
+  confuse(b2).text = confuse('four');
 
-  Expect.equals('three', inscrutable(b1).text);
-  Expect.equals('four', inscrutable(b2).text);
+  Expect.equals('three', confuse(b1).text);
+  Expect.equals('four', confuse(b2).text);
 
-  Expect.equals('foo:three', inscrutable(b1).foo());
-  Expect.equals('foo:four', inscrutable(b2).foo());
+  Expect.equals('foo:three', confuse(b1).foo());
+  Expect.equals('foo:four', confuse(b2).foo());
 }
 
 testSuperOnSubclassOfNative() {
   BB b1 = makeBB();
   BB b2 = makeBB();
 
   var constructor = findConstructorForNativeSubclassType(BB, 'init');
   Expect.isNotNull(constructor);
   JS('', '#(#)', constructor, b1);
   JS('', '#(#)', constructor, b2);
 
-  b1.afield = inscrutable('one');
-  b2.afield = inscrutable('two');
+  b1.afield = confuse('one');
+  b2.afield = confuse('two');
 
-  print('b1.afield ${inscrutable(b1).afield}');
-  print('b2.afield ${inscrutable(b2).afield}');
+  print('b1.afield ${confuse(b1).afield}');
+  print('b2.afield ${confuse(b2).afield}');
 
-  print('b1.afun() ${inscrutable(b1).afun()}');
-  print('b2.afun() ${inscrutable(b2).afun()}');
+  print('b1.afun() ${confuse(b1).afun()}');
+  print('b2.afun() ${confuse(b2).afun()}');
 
   Expect.equals('one', b1.afield);
   Expect.equals('two', b2.afield);
 
   Expect.equals('afun:one', b1.afun());
   Expect.equals('afun:two', b2.afun());
 
-  inscrutable(b1).afield = inscrutable('three');
-  inscrutable(b2).afield = inscrutable('four');
+  confuse(b1).afield = confuse('three');
+  confuse(b2).afield = confuse('four');
 
-  Expect.equals('three', inscrutable(b1).afield);
-  Expect.equals('four', inscrutable(b2).afield);
+  Expect.equals('three', confuse(b1).afield);
+  Expect.equals('four', confuse(b2).afield);
 
-  Expect.equals('afun:three', inscrutable(b1).afun());
-  Expect.equals('afun:four', inscrutable(b2).afun());
+  Expect.equals('afun:three', confuse(b1).afun());
+  Expect.equals('afun:four', confuse(b2).afun());
 }
 
 main() {
+  nativeTesting();
   setup();
-  inscrutable = (x) => x;
 
   setNativeSubclassDispatchRecord(getBBPrototype(), findInterceptorForType(BB));
 
   testSuperOnNative();
   testSuperOnSubclassOfNative();
 }