Remove #pragma once from ash

ash/wm/user_activity_detector.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_WM_USER_ACTIVITY_DETECTOR_H_
 #define ASH_WM_USER_ACTIVITY_DETECTOR_H_
-#pragma once
 
 #include "ash/ash_export.h"
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "base/observer_list.h"
 #include "base/time.h"
 #include "ui/aura/event_filter.h"
 
 namespace ash {
 
@@ skipping 40 matching lines @@
   // If set, used when the current time is needed.  This can be set by tests to
   // simulate the passage of time.
   base::TimeTicks now_for_test_;
 
   DISALLOW_COPY_AND_ASSIGN(UserActivityDetector);
 };
 
 }  // namespace ash
 
 #endif  // ASH_WM_USER_ACTIVITY_DETECTOR_H_