Prefer ScopedNestableTaskAllower over manual save/restore

ui/views/controls/menu/menu_controller.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 "ui/views/controls/menu/menu_controller.h"
 
 #include "base/i18n/case_conversion.h"
 #include "base/i18n/rtl.h"
 #include "base/time.h"
 #include "base/utf_string_conversions.h"
@@ skipping 304 matching lines @@
   if (ViewsDelegate::views_delegate)
     ViewsDelegate::views_delegate->AddRef();
 
   // We need to turn on nestable tasks as in some situations (pressing alt-f for
   // one) the menus are run from a task. If we don't do this and are invoked
   // from a task none of the tasks we schedule are processed and the menu
   // appears totally broken.
 #if defined(USE_AURA)
   aura::client::GetDispatcherClient()->RunWithDispatcher(this, true);
 #else
-  MessageLoopForUI* loop = MessageLoopForUI::current();
-  bool did_allow_task_nesting = loop->NestableTasksAllowed();
-  loop->SetNestableTasksAllowed(true);
-  loop->RunWithDispatcher(this);
-  loop->SetNestableTasksAllowed(did_allow_task_nesting);
+  {
+    MessageLoopForUI* loop = MessageLoopForUI::current();
+    MessageLoop::ScopedNestableTaskAllower allow(loop);
+    loop->RunWithDispatcher(this);
+  }
 #endif
 
   if (ViewsDelegate::views_delegate)
     ViewsDelegate::views_delegate->ReleaseRef();
 
   // Close any open menus.
   SetSelection(NULL, SELECTION_UPDATE_IMMEDIATELY | SELECTION_EXIT);
 
   if (nested_menu) {
     DCHECK(!menu_stack_.empty());
@@ skipping 1682 matching lines @@
              (!pending_state_.item->HasSubmenu() ||
               !pending_state_.item->GetSubmenu()->IsShowing())) {
     // On exit if the user hasn't selected an item with a submenu, move the
     // selection back to the parent menu item.
     SetSelection(pending_state_.item->GetParentMenuItem(),
                  SELECTION_OPEN_SUBMENU);
   }
 }
 
 }  // namespace views