Convert //ash from scoped_ptr to std::unique_ptr

ash/drag_drop/drag_drop_tracker.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_DRAG_DROP_DRAG_DROP_TRACKER_H_
 #define ASH_DRAG_DROP_DRAG_DROP_TRACKER_H_
 
+#include <memory>
+
 #include "ash/ash_export.h"
 #include "base/macros.h"
-#include "base/memory/scoped_ptr.h"
 #include "ui/events/event.h"
 
 namespace aura {
 class Window;
 class WindowDelegate;
 }
 
 namespace ash {
 
 // Provides functions for handling drag events inside and outside the root
@@ skipping 19 matching lines @@
   aura::Window* GetTarget(const ui::LocatedEvent& event);
 
   // Converts the locations of |event| in the coordinates of the active root
   // window to the ones in |target|'s coordinates.
   // Caller takes ownership of the returned object.
   ui::LocatedEvent* ConvertEvent(aura::Window* target,
                                  const ui::LocatedEvent& event);
 
  private:
   // A window for capturing drag events while dragging.
-  scoped_ptr<aura::Window> capture_window_;
+  std::unique_ptr<aura::Window> capture_window_;
 
   DISALLOW_COPY_AND_ASSIGN(DragDropTracker);
 };
 
 }  // namespace ash
 
 #endif  // ASH_DRAG_DROP_DRAG_DROP_TRACKER_H_