Wrap harmony implementations in functions.

src/harmony-spread.js

Index: src/harmony-spread.js
diff --git a/src/harmony-spread.js b/src/harmony-spread.js
index 48972fad08ec48ed37bef4b8a04d56916da56a55..5a511dd3a19008f5d93e6c04b533682464a1f011 100644
--- a/src/harmony-spread.js
+++ b/src/harmony-spread.js
@@ -2,6 +2,11 @@
 // 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() {
+
 'use strict';
 
 function SpreadArguments() {
@@ -31,3 +36,8 @@ function SpreadIterable(collection) {
   }
   return args;
 }
+
+$spreadArguments = SpreadArguments;
+$spreadIterable = SpreadIterable;
+
+})();