Call JS functions via native context instead of js builtins object.

src/harmony-spread.js

 // 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.
 
-var $spreadArguments;
-var $spreadIterable;
-
 (function(global, utils) {
 
 'use strict';
 
 // -------------------------------------------------------------------
 // Imports
 var InternalArray = utils.InternalArray;
 
 // -------------------------------------------------------------------
 
@@ skipping 18 matching lines @@
     throw MakeTypeError(kNotIterable, collection);
   }
 
   var args = new InternalArray();
   for (var value of collection) {
     args.push(value);
   }
   return args;
 }
 
-$spreadArguments = SpreadArguments;
-$spreadIterable = SpreadIterable;
+// ----------------------------------------------------------------------------
+// Exports
+
+%InstallToContext([
+  "spread_arguments", SpreadArguments,
+  "spread_iterable", SpreadIterable,
+]);
 
 })