Start removing some pre-md constants and related code.

ash/common/system/tray/system_tray_item.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 ASH_COMMON_SYSTEM_TRAY_SYSTEM_TRAY_ITEM_H_
 #define ASH_COMMON_SYSTEM_TRAY_SYSTEM_TRAY_ITEM_H_
 
 #include <memory>
 
 #include "ash/ash_export.h"
 #include "ash/common/login_status.h"
 #include "ash/public/cpp/shelf_types.h"
 #include "base/macros.h"
-
-namespace base {
-class OneShotTimer;
-}  // namespace base
+#include "base/timer/timer.h"
 
 namespace views {
 class View;
 }
 
 namespace ash {
 class SystemTray;
 class SystemTrayBubble;
 class TrayItemView;
 
@@ skipping 119 matching lines @@
   // the shelf is in the auto-hide state. Default is true.
   virtual bool ShouldShowShelf() const;
 
   // Returns the system tray that this item belongs to.
   SystemTray* system_tray() const { return system_tray_; }
 
   bool restore_focus() const { return restore_focus_; }
   void set_restore_focus(bool restore_focus) { restore_focus_ = restore_focus; }
 
  private:
-  // Actually transitions to the detailed view.
-  void DoTransitionToDetailedView();
-
   // Accesses uma_type().
   friend class SystemTrayBubble;
 
   UmaType uma_type() const { return uma_type_; }
 
   SystemTray* system_tray_;
   UmaType uma_type_;
   bool restore_focus_;
 
   // Used to delay the transition to the detailed view.
-  std::unique_ptr<base::OneShotTimer> transition_delay_timer_;
+  base::OneShotTimer transition_delay_timer_;
 
   DISALLOW_COPY_AND_ASSIGN(SystemTrayItem);
 };
 
 }  // namespace ash
 
 #endif  // ASH_COMMON_SYSTEM_TRAY_SYSTEM_TRAY_ITEM_H_