Convert //ash from scoped_ptr to std::unique_ptr

ash/system/date/tray_date.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_SYSTEM_DATE_TRAY_DATE_H_
 #define ASH_SYSTEM_DATE_TRAY_DATE_H_
 
+#include <memory>
+
 #include "ash/ash_export.h"
 #include "ash/system/date/clock_observer.h"
 #include "ash/system/tray/system_tray_item.h"
 #include "base/macros.h"
-#include "base/memory/scoped_ptr.h"
 
 namespace views {
 class Label;
 }
 
 namespace ash {
 class DateDefaultView;
 #if defined(OS_CHROMEOS)
 class SystemClockObserver;
 #endif
@@ skipping 42 matching lines @@
   void OnSystemClockCanSetTimeChanged(bool can_set_time) override;
   void Refresh() override;
 
   void SetupLabelForTimeTray(views::Label* label);
 
   tray::TimeView* time_tray_;
   DateDefaultView* default_view_;
   user::LoginStatus login_status_;
 
 #if defined(OS_CHROMEOS)
-  scoped_ptr<SystemClockObserver> system_clock_observer_;
+  std::unique_ptr<SystemClockObserver> system_clock_observer_;
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(TrayDate);
 };
 
 }  // namespace ash
 
 #endif  // ASH_SYSTEM_DATE_TRAY_DATE_H_