[modules] Define @@toStringTag on namespace object as a field.

src/objects-printer.cc

 // Copyright 2012 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.
 
 #include "src/objects.h"
 
 #include <iomanip>
 #include <memory>
 
 #include "src/bootstrapper.h"
@@ skipping 1271 matching lines @@
 void Module::ModulePrint(std::ostream& os) {  // NOLINT
   HeapObject::PrintHeader(os, "Module");
   os << "\n - code: " << Brief(code());
   os << "\n - exports: " << Brief(exports());
   os << "\n - requested_modules: " << Brief(requested_modules());
   os << "\n - evaluated: " << evaluated();
   os << "\n";
 }
 
 void JSModuleNamespace::JSModuleNamespacePrint(std::ostream& os) {  // NOLINT
-  HeapObject::PrintHeader(os, "JSModuleNamespace");
+  JSObjectPrintHeader(os, this, "JSModuleNamespace");
   os << "\n - module: " << Brief(module());
-  os << "\n";
+  JSObjectPrintBody(os, this);
 }
 
 void PrototypeInfo::PrototypeInfoPrint(std::ostream& os) {  // NOLINT
   HeapObject::PrintHeader(os, "PrototypeInfo");
   os << "\n - weak cell: " << Brief(weak_cell());
   os << "\n - prototype users: " << Brief(prototype_users());
   os << "\n - registry slot: " << registry_slot();
   os << "\n - validity cell: " << Brief(validity_cell());
   os << "\n - object create map: " << Brief(object_create_map());
   os << "\n";
@@ skipping 404 matching lines @@
     printf("Not a transition array\n");
   } else {
     reinterpret_cast<i::TransitionArray*>(object)->Print();
   }
 }
 
 extern void _v8_internal_Print_StackTrace() {
   i::Isolate* isolate = i::Isolate::Current();
   isolate->PrintStack(stdout);
 }