dart2js_native tests: Migrate 'native STRING' to JS-calls - part 2/2

tests/compiler/dart2js_native/subclassing_5_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' show setNativeSubclassDispatchRecord;
 import 'dart:_interceptors' show Interceptor, findInterceptorForType;
 
 // Test type checks.
 
@@ skipping 21 matching lines @@
     var z = x as T;
     Expect.identical(x, z);
   }
 }
 
 makeB() native;
 
 @Creates('=Object')
 getBPrototype() native;
 
-void setup() native r"""
-function B() {}
-makeB = function(){return new B;};
-getBPrototype = function(){return B.prototype;};
-""";
+void setup() {
+  JS('', r"""
+(function(){
+  function B() {}
+  makeB = function(){return new B()};
+  getBPrototype = function(){return B.prototype;};
+})()""");
+}
 
 bool isCheckedMode() {
   var isChecked = false;
   assert(isChecked = true);
   return isChecked;
 }
 
 testIsI(x) {
   Expect.isTrue(x is I);
 }
@@ skipping 103 matching lines @@
     confuse(new Checks<M>().assignCheck)(b);
     confuse(new Checks<I>().assignCheck)(b);
 
     confuse(new Checks<B>().castCheck)(b);
     confuse(new Checks<A>().castCheck)(b);
     confuse(new Checks<N>().castCheck)(b);
     confuse(new Checks<M>().castCheck)(b);
     confuse(new Checks<I>().castCheck)(b);
   }
 }