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

tests/compiler/dart2js_native/native_missing_method1_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 {}
 
 A makeA() native;
 
-void setup() native """
-function A() {};
-A.prototype.foo = function() { return  99; }
-makeA = function() { return new A; }
-self.nativeConstructor(A);
-""";
+void setup() {
+  JS('', r"""
+(function(){
+  function A() {};
+  A.prototype.foo = function() { return  99; };
+  makeA = function() { return new A(); };
+  self.nativeConstructor(A);
+})()""");
+}
 
 class B {
   // We need to define a foo method so that dart2js sees it. Because the
   // only occurences of 'foo' is on B, a Dart class, no interceptor is used.  It
   // thinks all calls will either go to this method, or throw a
   // NoSuchMethodError. It is possible that the native class will shadow a
   // method, but it will not shadow 'foo' because the name is either 'mangled'
   // with the arity, or minified.
   foo() {
     return 42;
@@ skipping 15 matching lines @@
   Expect.throws(() => a.foo, (e) => e is NoSuchMethodError);
   Expect.throws(() => a.foo = 4, (e) => e is NoSuchMethodError);
 }
 
 main() {
   nativeTesting();
   setup();
   typedContext();
   untypedContext();
 }