Ensure that privates are private.

extensions/renderer/module_system.cc

 // Copyright 2014 The Chromium 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 "extensions/renderer/module_system.h"
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/logging.h"
 #include "base/macros.h"
@@ skipping 600 matching lines @@
   }
   v8::Local<v8::Object> obj = args[0].As<v8::Object>();
   v8::Local<v8::Value> privates;
   if (!GetPrivate(obj, "privates", &privates) || !privates->IsObject()) {
     privates = v8::Object::New(args.GetIsolate());
     if (privates.IsEmpty()) {
       GetIsolate()->ThrowException(
           ToV8StringUnsafe(GetIsolate(), "Failed to create privates"));
       return;
     }
+    v8::Maybe<bool> maybe =
+        privates.As<v8::Object>()->SetPrototype(context()->v8_context(),
+                                                v8::Null(args.GetIsolate()));
+    CHECK(maybe.IsJust() && maybe.FromJust());
     SetPrivate(obj, "privates", privates);
   }
   args.GetReturnValue().Set(privates);
 }
 
 v8::Local<v8::Value> ModuleSystem::LoadModule(const std::string& module_name) {
   v8::EscapableHandleScope handle_scope(GetIsolate());
   v8::Local<v8::Context> v8_context = context()->v8_context();
   v8::Context::Scope context_scope(v8_context);
 
@@ skipping 116 matching lines @@
 
 void ModuleSystem::ClobberExistingNativeHandler(const std::string& name) {
   NativeHandlerMap::iterator existing_handler = native_handler_map_.find(name);
   if (existing_handler != native_handler_map_.end()) {
     clobbered_native_handlers_.push_back(std::move(existing_handler->second));
     native_handler_map_.erase(existing_handler);
   }
 }
 
 }  // namespace extensions