Change dart2js_foreign suite to use metadata.

dart/tests/compiler/dart2js_foreign/native_null_closure_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.
 
 typedef void MyFunctionType();
 
-class A native "*A" {
-  setClosure(MyFunctionType f) native;
-  check(MyFunctionType f) native;
-  invoke() native;
+@native("*A")
+class A  {
+  @native setClosure(MyFunctionType f);
+  @native check(MyFunctionType f);
+  @native invoke();
 }
 
-makeA() native { return new A(); }
+@native makeA() { return new A(); }
 
-void setup() native """
+@native("""
 function A() {}
 A.prototype.setClosure = function(f) { this.f = f; };
 A.prototype.check = function(f) { return this.f === f; };
 A.prototype.invoke = function() { return this.f(); };
 makeA = function(){return new A;};
-""";
+""")
+void setup();
 
 
 main() {
   setup();
   A a = makeA();
   a.setClosure(null);
   Expect.isTrue(a.check(null));
   bool caughtException = false;
   try {
     a.invoke();
   } catch (Exception e) {
     caughtException = true;
   }
   Expect.isTrue(caughtException);
 }