ES6 symbols: Allow symbols as property names

src/proxy.js

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 171 matching lines @@
     }
   }
   return enumerableNames
 }
 
 function ProxyEnumerate(proxy) {
   var handler = %GetHandler(proxy)
   if (IS_UNDEFINED(handler.enumerate)) {
     return %Apply(DerivedEnumerateTrap, handler, [], 0, 0)
   } else {
-    return ToStringArray(handler.enumerate(), "enumerate")
+    return ToNameArray(handler.enumerate(), "enumerate")
   }
 }