Introduce extras export object.

test/cctest/test-extra.js

Index: test/cctest/test-extra.js
diff --git a/test/message/export-duplicate-as.js b/test/cctest/test-extra.js
similarity index 58%
copy from test/message/export-duplicate-as.js
copy to test/cctest/test-extra.js
index 49b52d4b17177e9443445f00379227cce07a034d..9c63d9c103836a714ab48f420d62c62fea44cb78 100644
--- a/test/message/export-duplicate-as.js
+++ b/test/cctest/test-extra.js
@@ -1,9 +1,10 @@
 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
-//
-// MODULE
 
-var a, b;
-export { a as c };
-export { a, b as c };
+(function (global, exports) {
+  'use strict';
+  exports.testExtraShouldReturnFive = function () {
+    return 5;
+  };
+})