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

src/harmony-spread.js

Index: src/harmony-spread.js
diff --git a/src/harmony-spread.js b/src/harmony-spread.js
index bfd6acb3a1eaa3119cfc8117250d441a55425897..b271c7efe54e1ec114b66344f275adfe4be98761 100644
--- a/src/harmony-spread.js
+++ b/src/harmony-spread.js
@@ -2,9 +2,6 @@
 // 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';
@@ -43,7 +40,12 @@ function SpreadIterable(collection) {
   return args;
 }
 
-$spreadArguments = SpreadArguments;
-$spreadIterable = SpreadIterable;
+// ----------------------------------------------------------------------------
+// Exports
+
+%InstallToContext([
+  "spread_arguments", SpreadArguments,
+  "spread_iterable", SpreadIterable,
+]);
 
 })