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

src/generator.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.
 
 (function(global, utils) {
 
 "use strict";
 
 %CheckIsBootstrapping();
 
 // -------------------------------------------------------------------
 // Imports
 
 var GlobalFunction = global.Function;
-
 var NewFunctionString;
+var toStringTagSymbol = utils.ImportNow("to_string_tag_symbol");
 
 utils.Import(function(from) {
   NewFunctionString = from.NewFunctionString;
 });
 
 // ----------------------------------------------------------------------------
 
 // Generator functions and objects are specified by ES6, sections 15.19.3 and
 // 15.19.4.
 
@@ skipping 68 matching lines @@
 // Set up non-enumerable functions on the generator prototype object.
 var GeneratorObjectPrototype = GeneratorFunctionPrototype.prototype;
 utils.InstallFunctions(GeneratorObjectPrototype,
                        DONT_ENUM,
                       ["next", GeneratorObjectNext,
                        "throw", GeneratorObjectThrow]);
 
 %AddNamedProperty(GeneratorObjectPrototype, "constructor",
     GeneratorFunctionPrototype, DONT_ENUM | READ_ONLY);
 %AddNamedProperty(GeneratorObjectPrototype,
-    symbolToStringTag, "Generator", DONT_ENUM | READ_ONLY);
+    toStringTagSymbol, "Generator", DONT_ENUM | READ_ONLY);
 %InternalSetPrototype(GeneratorFunctionPrototype, GlobalFunction.prototype);
 %AddNamedProperty(GeneratorFunctionPrototype,
-    symbolToStringTag, "GeneratorFunction", DONT_ENUM | READ_ONLY);
+    toStringTagSymbol, "GeneratorFunction", DONT_ENUM | READ_ONLY);
 %AddNamedProperty(GeneratorFunctionPrototype, "constructor",
     GeneratorFunction, DONT_ENUM | READ_ONLY);
 %InternalSetPrototype(GeneratorFunction, GlobalFunction);
 %SetCode(GeneratorFunction, GeneratorFunctionConstructor);
 
 })