Extract the view of control buttons on notification into a separated class

ui/message_center/views/message_view.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_MESSAGE_CENTER_VIEWS_MESSAGE_VIEW_H_
 #define UI_MESSAGE_CENTER_VIEWS_MESSAGE_VIEW_H_
 
 #include <memory>
 
 #include "base/macros.h"
@@ skipping 42 matching lines @@
   static gfx::Insets GetShadowInsets();
 
   // Creates a shadow around the notification and changes slide-out behavior.
   void SetIsNested();
 
   virtual bool IsCloseButtonFocused() const = 0;
   virtual void RequestFocusOnCloseButton() = 0;
   virtual void UpdateControlButtonsVisibility() = 0;
 
   void OnCloseButtonPressed();
+  void OnSettingsButtonPressed();
 
   // views::View
   void GetAccessibleNodeData(ui::AXNodeData* node_data) override;
   bool OnMousePressed(const ui::MouseEvent& event) override;
   bool OnKeyPressed(const ui::KeyEvent& event) override;
   bool OnKeyReleased(const ui::KeyEvent& event) override;
   void OnPaint(gfx::Canvas* canvas) override;
   void OnFocus() override;
   void OnBlur() override;
   void Layout() override;
@@ skipping 47 matching lines @@
   // True if |this| is embedded in another view. Equivalent to |!top_level| in
   // MessageViewFactory parlance.
   bool is_nested_ = false;
 
   DISALLOW_COPY_AND_ASSIGN(MessageView);
 };
 
 }  // namespace message_center
 
 #endif // UI_MESSAGE_CENTER_VIEWS_MESSAGE_VIEW_H_