Remove pre-MD code from SystemTrayBubble.

ash/common/system/tray/tray_popup_item_container.h

-// Copyright (c) 2014 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 ASH_COMMON_SYSTEM_TRAY_TRAY_POPUP_ITEM_CONTAINER_H_
-#define ASH_COMMON_SYSTEM_TRAY_TRAY_POPUP_ITEM_CONTAINER_H_
-
-#include "base/macros.h"
-#include "ui/views/view.h"
-
-namespace ash {
-
-// A view which can optionally change the background color when a mouse is
-// hovering or a user is interacting via touch.
-class TrayPopupItemContainer : public views::View {
- public:
-  TrayPopupItemContainer(views::View* view, bool change_background);
-
-  ~TrayPopupItemContainer() override;
-
-  bool active() { return active_; }
-
- private:
-  // Sets whether the active background is to be used, and triggers a paint.
-  void SetActive(bool active);
-
-  // views::View:
-  void ChildVisibilityChanged(views::View* child) override;
-  void ChildPreferredSizeChanged(views::View* child) override;
-  void OnMouseEntered(const ui::MouseEvent& event) override;
-  void OnMouseExited(const ui::MouseEvent& event) override;
-  void OnGestureEvent(ui::GestureEvent* event) override;
-  void OnPaintBackground(gfx::Canvas* canvas) override;
-
-  // True if either a mouse is hovering over this view, or if a user has touched
-  // down.
-  bool active_;
-
-  // True if mouse hover and touch feedback can alter the background color of
-  // the container.
-  bool change_background_;
-
-  DISALLOW_COPY_AND_ASSIGN(TrayPopupItemContainer);
-};
-
-}  // namespace ash
-
-#endif  // ASH_COMMON_SYSTEM_TRAY_TRAY_POPUP_ITEM_CONTAINER_H_