Prefer ScopedNestableTaskAllower over manual save/restore

chrome/browser/ui/views/simple_message_box_views.cc

 // Copyright (c) 2012 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 "chrome/browser/ui/views/simple_message_box_views.h"
 
 #include "base/utf_string_conversions.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/simple_message_box.h"
 #include "chrome/browser/ui/dialog_style.h"
@@ skipping 45 matching lines @@
   scoped_refptr<SimpleMessageBoxViews> dialog =
       new SimpleMessageBoxViews(parent_window, DIALOG_YES_NO, title, message);
 
   // Make sure Chrome doesn't attempt to shut down with the dialog up.
   g_browser_process->AddRefModule();
 
 #if defined(USE_AURA)
   aura::client::GetDispatcherClient()->RunWithDispatcher(dialog,
       parent_window, true);
 #else
-  bool old_state = MessageLoopForUI::current()->NestableTasksAllowed();
-  MessageLoopForUI::current()->SetNestableTasksAllowed(true);
-  MessageLoopForUI::current()->RunWithDispatcher(dialog);
-  MessageLoopForUI::current()->SetNestableTasksAllowed(old_state);
+  {
+    MessageLoop::ScopedNestableTaskAllower allow(MessageLoopForUI::current());
+    MessageLoopForUI::current()->RunWithDispatcher(dialog);
+  }
 #endif
 
   g_browser_process->ReleaseModule();
 
   return dialog->Accepted();
 }
 
 bool SimpleMessageBoxViews::Cancel() {
   disposition_ = DISPOSITION_CANCEL;
   return true;
@@ skipping 82 matching lines @@
   if (disposition_ == DISPOSITION_UNKNOWN)
     return base::MessagePumpDispatcher::EVENT_PROCESSED;
   return base::MessagePumpDispatcher::EVENT_QUIT;
 }
 #else
 bool SimpleMessageBoxViews::Dispatch(GdkEvent* event) {
   gtk_main_do_event(event);
   return disposition_ == DISPOSITION_UNKNOWN;
 }
 #endif