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

tests/compiler/dart2js_native/native_constructor_name_test.dart

Index: tests/compiler/dart2js_native/native_constructor_name_test.dart
diff --git a/tests/compiler/dart2js_native/native_constructor_name_test.dart b/tests/compiler/dart2js_native/native_constructor_name_test.dart
index 5582e842b48f1fd0435bf4e7166b9a7089010793..dbe9984a53b58113c9a5553d5c9476a924c6f662 100644
--- a/tests/compiler/dart2js_native/native_constructor_name_test.dart
+++ b/tests/compiler/dart2js_native/native_constructor_name_test.dart
@@ -19,11 +19,14 @@ class Z {
 
 makeZ() native;
 
-void setup() native """
-function A(){}
-makeZ = function(){return new A};
-self.nativeConstructor(A);
-""";
+void setup() {
+  JS('', r"""
+(function(){
+  function A(){}
+  makeZ = function(){return new A()};
+  self.nativeConstructor(A);
+})()""");
+}
 
 main() {
   nativeTesting();