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

tests/compiler/dart2js_native/subclassing_super_field_1_test.dart

Index: tests/compiler/dart2js_native/subclassing_super_field_1_test.dart
diff --git a/tests/compiler/dart2js_native/subclassing_super_field_1_test.dart b/tests/compiler/dart2js_native/subclassing_super_field_1_test.dart
index 75f6a68e556c082d1d13a3f47fe8fbf95644058a..827cb358812fa9bba2f09476a10dfdb6881dfa44 100644
--- a/tests/compiler/dart2js_native/subclassing_super_field_1_test.dart
+++ b/tests/compiler/dart2js_native/subclassing_super_field_1_test.dart
@@ -32,12 +32,15 @@ B makeB() native;
 @Creates('=Object')
 getBPrototype() native;
 
-void setup() native r"""
+void setup() {
+  JS('', r"""
+(function(){
 function B() { }
-makeB = function(){return new B;};
+makeB = function(){return new B()};
 
 getBPrototype = function(){return B.prototype;};
-""";
+})()""");
+}
 
 main() {
   nativeTesting();