Revert "Add native_testing library to mock @Native classes"

tests/compiler/dart2js_native/native_missing_method1_frog_test.dart

 // Copyright (c) 2012, 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 {}
 
-A makeA() native ;
+makeA() native ;
 
 void setup() native """
 function A() {};
-A.prototype.foo = function() { return  99; }
+A.prototype.foo = function() { return  42; }
 makeA = function() { return new A; }
-self.nativeConstructor(A);
 """;
 
 class B {
-  // We need to define a foo method so that dart2js sees it. Because the the
-  // only occurences of 'foo' is on B, a Dart class, no interceptor is used.  It
-  // thinks all calls will either go to this method, or throw a
-  // NoSuchMethodError. It is possible that the native class will shadow a
-  // method, but it will not shadow 'foo' because the name is either 'mangled'
-  // with the arity, or minified.
+  // We need to define a foo method so that Frog sees it. Because it's
+  // the only occurence of 'foo', Frog does not bother mangling the
+  // call sites. It thinks all calls will either go to this method, or
+  // throw a NoSuchMethodError.
   foo() {
     return 42;
   }
 }
 
 typedContext() {
-  confuse(new B()).foo();
-  A a = makeA();
+  var things = [makeA(), new B()];
+  A a = things[0];
   Expect.throws(() => a.foo(), (e) => e is NoSuchMethodError);
   Expect.throws(() => a.foo, (e) => e is NoSuchMethodError);
   Expect.throws(() => a.foo = 4, (e) => e is NoSuchMethodError);
 }
 
 untypedContext() {
-  confuse(new B()).foo();
-  var a = confuse(makeA());
+  var things = [makeA(), new B()];
+  var a = things[0];
   Expect.throws(() => a.foo(), (e) => e is NoSuchMethodError);
   Expect.throws(() => a.foo, (e) => e is NoSuchMethodError);
   Expect.throws(() => a.foo = 4, (e) => e is NoSuchMethodError);
 }
 
 main() {
-  nativeTesting();
   setup();
   typedContext();
   untypedContext();
 }