Make SystemMonitor not a Singleton and move it out of base

app/system_monitor.h

 // Copyright (c) 2009 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_
+#ifndef APP_SYSTEM_MONITOR_H_
+#define APP_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"
 #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:
-  // Retrieves the Singleton.
+  // Create SystemMonitor. Only one SystemMonitor instance per application
+  // is allowed.
+  SystemMonitor();
+  ~SystemMonitor();
+
+  // Get the application-wide SystemMonitor (if not present, returns NULL).
   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();
-
   //
   // Power-related APIs
   //
 
   // Is the computer currently on battery power.
   // Can be called on any thread.
   bool BatteryPower() const {
     // Using a lock here is not necessary for just a bool.
     return battery_in_use_;
   }
@@ skipping 36 matching lines @@
 #if defined(OS_WIN)
   // Windows-specific handling of a WM_POWERBROADCAST message.
   // Embedders of this API should hook their top-level window
   // message loop and forward WM_POWERBROADCAST through this call.
   void ProcessWmPowerBroadcastMessage(int event_id);
 #endif
 
   // Cross-platform handling of a power event.
   void ProcessPowerMessage(PowerEvent event_id);
 
-  // Constructor.
-  // Don't use this; access SystemMonitor via the Singleton.
-  SystemMonitor();
-
  private:
   // Platform-specific method to check whether the system is currently
   // running on battery power.  Returns true if running on batteries,
   // false otherwise.
   bool IsBatteryPower();
 
   // Checks the battery status and notifies observers if the battery
   // status has changed.
   void BatteryCheck();
 
   // Functions to trigger notifications.
   void NotifyPowerStateChange();
   void NotifySuspend();
   void NotifyResume();
 
   scoped_refptr<ObserverListThreadSafe<PowerObserver> > observer_list_;
   bool battery_in_use_;
   bool suspended_;
 
 #if defined(ENABLE_BATTERY_MONITORING)
   base::OneShotTimer<SystemMonitor> delayed_battery_check_;
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(SystemMonitor);
 };
 
-}
-
-#endif  // BASE_SYSTEM_MONITOR_H_
+#endif  // APP_SYSTEM_MONITOR_H_