Simple cleanup.

base/system_monitor.h

 // Copyright (c) 2008 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_SYSTEM_MONITOR_H_
 #define BASE_SYSTEM_MONITOR_H_
 
 #include "build/build_config.h"
 
 // Windows HiRes timers drain the battery faster so we need to know the battery
 // status.  This isn't true for other platforms.
 #if defined(OS_WIN)
 #define ENABLE_BATTERY_MONITORING 1
 #else
 #undef ENABLE_BATTERY_MONITORING
 #endif  // !OS_WIN
 
 #include "base/observer_list_threadsafe.h"
-#include "base/singleton.h"
 #if defined(ENABLE_BATTERY_MONITORING)
 #include "base/timer.h"
 #endif  // defined(ENABLE_BATTERY_MONITORING)
 
 namespace base {
 
 // Class for monitoring various system-related subsystems
 // such as power management, network status, etc.
 // TODO(mbelshe):  Add support beyond just power management.
 class SystemMonitor {
  public:
-  // Access to the Singleton
-  static SystemMonitor* Get() {
-    // Uses the LeakySingletonTrait because cleanup is optional.
-    return
-        Singleton<SystemMonitor, LeakySingletonTraits<SystemMonitor> >::get();
-  }
+  // Retrieves the Singleton.
+  static SystemMonitor* Get();
 
   // Start the System Monitor within a process.  This method
   // is provided so that the battery check can be deferred.
   // The MessageLoop must be started before calling this
   // method.
   // This is a no-op on platforms for which ENABLE_BATTERY_MONITORING is
   // disabled.
   static void Start();
 
   //
@@ skipping 13 matching lines @@
     SUSPEND_EVENT,      // The system is being suspended.
     RESUME_EVENT        // The system is being resumed.
   };
 
   // Callbacks will be called on the thread which creates the SystemMonitor.
   // During the callback, Add/RemoveObserver will block until the callbacks
   // are finished. Observers should implement quick callback functions; if
   // lengthy operations are needed, the observer should take care to invoke
   // the operation on an appropriate thread.
   class PowerObserver {
-  public:
+   public:
     // Notification of a change in power status of the computer, such
     // as from switching between battery and A/C power.
     virtual void OnPowerStateChange(SystemMonitor*) = 0;
 
     // Notification that the system is suspending.
     virtual void OnSuspend(SystemMonitor*) = 0;
 
     // Notification that the system is resuming.
     virtual void OnResume(SystemMonitor*) = 0;
   };
@@ skipping 44 matching lines @@
 #if defined(ENABLE_BATTERY_MONITORING)
   base::OneShotTimer<SystemMonitor> delayed_battery_check_;
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(SystemMonitor);
 };
 
 }
 
 #endif  // BASE_SYSTEM_MONITOR_H_