Remove #pragma once. Just from base/ for now.

base/hi_res_timer_manager.h

 // Copyright (c) 2011 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 BASE_HI_RES_TIMER_MANAGER_H_
 #define BASE_HI_RES_TIMER_MANAGER_H_
-#pragma once
 
 #include "base/base_export.h"
 #include "base/system_monitor/system_monitor.h"
 
 // Ensures that the Windows high resolution timer is only used
 // when not running on battery power.
 class BASE_EXPORT HighResolutionTimerManager
     : public base::SystemMonitor::PowerObserver {
  public:
   HighResolutionTimerManager();
   virtual ~HighResolutionTimerManager();
 
   // base::SystemMonitor::PowerObserver:
   virtual void OnPowerStateChange(bool on_battery_power) OVERRIDE;
 
   // Returns true if the hi resolution clock could be used right now.
   bool hi_res_clock_available() const { return hi_res_clock_available_; }
 
  private:
   // Enable or disable the faster multimedia timer.
   void UseHiResClock(bool use);
 
   bool hi_res_clock_available_;
 
   DISALLOW_COPY_AND_ASSIGN(HighResolutionTimerManager);
 };
 
 #endif  // BASE_HI_RES_TIMER_MANAGER_H_