dart2js_native tests: Migrate 'native STRING' to JS-calls

tests/compiler/dart2js_native/native_method_with_keyword_name_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';
 
 // Make sure we can have a native with a name that is a JavaScript keyword.
 
 @Native("A")
 class A {
   int delete() native;
 }
 
 A makeA() native;
 
-void setup() native """
+void setup() {
+  JS('', r"""
+(function(){
 function A() {}
 A.prototype.delete = function() { return 87; };
 
-makeA = function(){return new A;};
+makeA = function(){return new A()};
 self.nativeConstructor(A);
-""";
+})()""");
+}
 
 main() {
   nativeTesting();
   setup();
 
   var a1 = confuse(makeA());
   Expect.equals(87, a1.delete());
   A a2 = makeA();
   Expect.equals(87, a2.delete());
 }