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

tests/compiler/dart2js_native/native_no_such_method_exception2_frog_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";
 
 @Native("A")
 class A {}
 
 @Native("B")
 class B extends A {
   foo() native;
 }
 
 makeA() native;
 makeB() native;
 
-setup() native """
-function inherits(child, parent) {
-  if (child.prototype.__proto__) {
-    child.prototype.__proto__ = parent.prototype;
-  } else {
-    function tmp() {};
-    tmp.prototype = parent.prototype;
-    child.prototype = new tmp();
-    child.prototype.constructor = child;
+setup() {
+  JS('', r"""
+(function(){
+  function inherits(child, parent) {
+    if (child.prototype.__proto__) {
+      child.prototype.__proto__ = parent.prototype;
+    } else {
+      function tmp() {};
+      tmp.prototype = parent.prototype;
+      child.prototype = new tmp();
+      child.prototype.constructor = child;
+    }
   }
+    function A() {}
+    function B() {}
+    inherits(B, A);
+    makeA = function() { return new A() };
+    makeB = function() { return new B() };
+    B.prototype.foo = function() { return 42; };
+
+    self.nativeConstructor(A);
+    self.nativeConstructor(B);
+})()""");
 }
-  function A() {}
-  function B() {}
-  inherits(B, A);
-  makeA = function() { return new A; }
-  makeB = function() { return new B; }
-  B.prototype.foo = function() { return 42; }
-
-  self.nativeConstructor(A);
-  self.nativeConstructor(B);
-""";
 
 main() {
   nativeTesting();
   setup();
   var a = makeA();
   var exception;
   try {
     a.foo();
   } on NoSuchMethodError catch (e) {
     exception = e;
   }
   Expect.isNotNull(exception);
 
   var b = makeB();
   Expect.equals(42, b.foo());
 }