Use a single views::MenuConfig instance for each platform

ui/views/controls/combobox/combobox.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/combobox/combobox.h"
 
 #include "base/logging.h"
 #include "ui/accessibility/ax_view_state.h"
 #include "ui/base/ime/input_method.h"
 #include "ui/base/models/combobox_model.h"
@@ skipping 215 matching lines @@
   ComboboxMenuModelAdapter(Combobox* owner, ui::ComboboxModel* model)
       : owner_(owner), model_(model) {
     model_->AddObserver(this);
   }
 
   ~ComboboxMenuModelAdapter() override { model_->RemoveObserver(this); }
 
  private:
   bool UseCheckmarks() const {
     return owner_->style_ != STYLE_ACTION &&
-           MenuConfig::instance(owner_->GetNativeTheme())
-               .check_selected_combobox_item;
+           MenuConfig::instance().check_selected_combobox_item;
   }
 
   // Overridden from MenuModel:
   bool HasIcons() const override { return false; }
 
   int GetItemCount() const override { return model_->GetItemCount(); }
 
   ItemType GetTypeAt(int index) const override {
     if (model_->IsItemSeparatorAt(index)) {
       // In action menus, disallow <item>, <separator>, ... since that would put
@@ skipping 673 matching lines @@
   return gfx::Size(width, font_list.GetHeight());
 }
 
 PrefixSelector* Combobox::GetPrefixSelector() {
   if (!selector_)
     selector_.reset(new PrefixSelector(this));
   return selector_.get();
 }
 
 }  // namespace views