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

tests/compiler/dart2js_native/native_class_avoids_hidden_name_frog_test.dart

 // Copyright (c) 2011, 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";
 
 // Test that hidden native class names are not used by generated code.
 
 @Native("BB")
 class AA {
   get name => 'AA';
   static AA create() => makeA();
 }
 
 @Native("CC")
 class BB {
   get name => 'BB';
   static BB create() => makeB();
 }
 
 class CC {
   // Ordinary class with name clashing with native class.
   get name => 'CC';
   static CC create() => new CC();
 }
 
 makeA() native;
 makeB() native;
 
-void setup1() native """
-// Poison hidden native names 'BB' and 'CC' to prove the compiler didn't place
-// anything on the hidden native class.
-BB = null;
-CC = null;
-""";
+void setup1() {
+  JS('', r"""
+(function(){
+  // Poison hidden native names 'BB' and 'CC' to prove the compiler didn't place
+  // anything on the hidden native class.
+  BB = null;
+  CC = null;
+})()""");
+}
 
-void setup2() native """
-// This code is all inside 'setup' and so not accessible from the global scope.
-function BB(){}
-function CC(){}
-makeA = function(){return new BB};  // AA is native "BB"
-makeB = function(){return new CC};  // BB is native "CC"
-self.nativeConstructor(BB);
-self.nativeConstructor(CC);
-""";
+void setup2() {
+  JS('', r"""
+(function(){
+  // This code is inside 'setup' and so not accessible from the global scope.
+  function BB(){}
+  function CC(){}
+  makeA = function(){return new BB()};  // AA is native "BB"
+  makeB = function(){return new CC()};  // BB is native "CC"
+  self.nativeConstructor(BB);
+  self.nativeConstructor(CC);
+})()""");
+}
 
 main() {
   nativeTesting();
   setup1();
   setup2();
 
   var a = confuse(AA.create());
   var b = confuse(BB.create());
   var c = confuse(CC.create());
 
   Expect.equals('AA', a.name);
   Expect.equals('BB', b.name);
   Expect.equals('CC', c.name);
 }