Native context: do not put public symbols and flags on the js builtins object.

src/runtime.js

 // Copyright 2006-2008 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.
 
 // This files contains runtime support implemented in JavaScript.
 
 // CAUTION: Some of the functions specified in this file are called
 // directly from compiled code. These are the functions with names in
 // ALL CAPS. The compiled code passes the first argument in 'this'.
 
@@ skipping 15 matching lines @@
 var $toString;
 
 (function(global, utils) {
 
 %CheckIsBootstrapping();
 
 var GlobalArray = global.Array;
 var GlobalBoolean = global.Boolean;
 var GlobalString = global.String;
 var GlobalNumber = global.Number;
+var isConcatSpreadableSymbol =
+    utils.ImportNow("is_concat_spreadable_symbol");
 
 // ----------------------------------------------------------------------------
 
 /* -----------------------------------
 - - -   C o m p a r i s o n   - - -
 -----------------------------------
 */
 
 // ECMA-262 Section 11.9.3.
 function EQUALS(y) {
@@ skipping 712 matching lines @@
   // Even though the type of null is "object", null is still
   // considered a primitive value. IS_SPEC_OBJECT handles this correctly
   // (i.e., it will return false if x is null).
   return !IS_SPEC_OBJECT(x);
 }
 
 
 // ES6, draft 10-14-14, section 22.1.3.1.1
 function IsConcatSpreadable(O) {
   if (!IS_SPEC_OBJECT(O)) return false;
-  var spreadable = O[symbolIsConcatSpreadable];
+  var spreadable = O[isConcatSpreadableSymbol];
   if (IS_UNDEFINED(spreadable)) return IS_ARRAY(O);
   return ToBoolean(spreadable);
 }
 
 
 // ECMA-262, section 8.6.2.6, page 28.
 function DefaultNumber(x) {
   var valueOf = x.valueOf;
   if (IS_SPEC_FUNCTION(valueOf)) {
     var v = %_CallFunction(x, valueOf);
@@ skipping 117 matching lines @@
 utils.Export(function(to) {
   to.ToBoolean = ToBoolean;
   to.ToLength = ToLength;
   to.ToName = ToName;
   to.ToNumber = ToNumber;
   to.ToPrimitive = ToPrimitive;
   to.ToString = ToString;
 });
 
 })