Introduce a type of View background that stays in sync with its host

ui/message_center/views/message_bubble_base.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_BUBBLE_BASE_H_
 #define UI_MESSAGE_CENTER_VIEWS_MESSAGE_BUBBLE_BASE_H_
 
 #include <memory>
 
 #include "base/macros.h"
@@ skipping 39 matching lines @@
   virtual void OnMouseExitedView() = 0;
 
   // Schedules bubble for layout after all notifications have been
   // added and icons have had a chance to load.
   void ScheduleUpdate();
 
   bool IsVisible() const;
 
   views::TrayBubbleView* bubble_view() const { return bubble_view_; }
 
-  static const SkColor kBackgroundColor;
-
  protected:
   views::TrayBubbleView::InitParams GetDefaultInitParams(
       views::TrayBubbleView::AnchorAlignment anchor_alignment);
   MessageCenter* message_center() { return message_center_; }
   MessageCenterTray* tray() { return tray_; }
   void set_bubble_view(views::TrayBubbleView* bubble_view) {
     bubble_view_ = bubble_view;
   }
 
  private:
   MessageCenter* message_center_;
   MessageCenterTray* tray_;
   views::TrayBubbleView* bubble_view_;
   int max_height_;
   base::WeakPtrFactory<MessageBubbleBase> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(MessageBubbleBase);
 };
 
 }  // namespace message_center
 
 #endif // UI_MESSAGE_CENTER_VIEWS_MESSAGE_BUBBLE_BASE_H_