Native context: debug.js does not load from js builtins object anymore.

src/symbol.js

 // Copyright 2013 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.
 
 // Expects following symbols to be set in the bootstrapper during genesis:
 // - symbolHasInstance
 // - symbolIsConcatSpreadable
 // - symbolIsRegExp
 // - symbolIterator
 // - symbolToStringTag
 // - symbolUnscopables
 
 var $symbolToString;
 
 (function(global, utils) {
 
 "use strict";
 
 %CheckIsBootstrapping();
 
 // -------------------------------------------------------------------
 // Imports
 
 var GlobalObject = global.Object;
 var GlobalSymbol = global.Symbol;
-
 var ObjectGetOwnPropertyKeys;
+var ToString;
 
 utils.Import(function(from) {
   ObjectGetOwnPropertyKeys = from.ObjectGetOwnPropertyKeys;
+  ToString = from.ToString;
 });
 
 // -------------------------------------------------------------------
 
 function SymbolConstructor(x) {
   if (%_IsConstructCall()) throw MakeTypeError(kNotConstructor, "Symbol");
   // NOTE: Passing in a Symbol value will throw on ToString().
-  return %CreateSymbol(IS_UNDEFINED(x) ? x : $toString(x));
+  return %CreateSymbol(IS_UNDEFINED(x) ? x : ToString(x));
 }
 
 
 function SymbolToString() {
   if (!(IS_SYMBOL(this) || IS_SYMBOL_WRAPPER(this))) {
     throw MakeTypeError(kIncompatibleMethodReceiver,
                         "Symbol.prototype.toString", this);
   }
   var description = %SymbolDescription(%_ValueOf(this));
   return "Symbol(" + (IS_UNDEFINED(description) ? "" : description) + ")";
@@ skipping 68 matching lines @@
   "valueOf", SymbolValueOf
 ]);
 
 utils.InstallFunctions(GlobalObject, DONT_ENUM, [
   "getOwnPropertySymbols", ObjectGetOwnPropertySymbols
 ]);
 
 $symbolToString = SymbolToString;
 
 })