Make notifier settings combobox a real combobox.

ui/base/models/combobox_model.h

 // 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.
 
 #ifndef UI_BASE_MODELS_COMBOBOX_MODEL_H_
 #define UI_BASE_MODELS_COMBOBOX_MODEL_H_
 
 #include "base/strings/string16.h"
 #include "ui/base/ui_base_export.h"
 
 namespace ui {
 
 class ComboboxModelObserver;
 
 // A data model for a combo box.
 class UI_BASE_EXPORT ComboboxModel {
  public:
+  virtual ~ComboboxModel() {}
+
   // Returns the number of items in the combo box.
   virtual int GetItemCount() const = 0;
 
   // Returns the string at the specified index.
   virtual base::string16 GetItemAt(int index) = 0;
 
   // Should return true if the item at |index| is a non-selectable separator
   // item.
   virtual bool IsItemSeparatorAt(int index);
 
   // The index of the item that is selected by default (before user
   // interaction).
   virtual int GetDefaultIndex() const;
 
   // Returns true if the item at |index| is enabled.
   virtual bool IsItemEnabledAt(int index) const;
 
   // Adds/removes an observer. Override if model supports mutation.
   virtual void AddObserver(ComboboxModelObserver* observer) {}
   virtual void RemoveObserver(ComboboxModelObserver* observer) {}
-
- protected:
-  virtual ~ComboboxModel() {}
 };
 
 }  // namespace ui
 
 #endif  // UI_BASE_MODELS_COMBOBOX_MODEL_H_