Attempting to resolve a race condition with PowerMonitor

base/power_monitor/power_monitor.h

Index: base/power_monitor/power_monitor.h
diff --git a/base/power_monitor/power_monitor.h b/base/power_monitor/power_monitor.h
index 4acb3bf122dba93633a1201631063810ef3e9d5d..712b6b3cd89baeb1341cd8caf7906a0f1d439115 100644
--- a/base/power_monitor/power_monitor.h
+++ b/base/power_monitor/power_monitor.h
@@ -10,6 +10,7 @@
 #include "base/memory/ref_counted.h"
 #include "base/observer_list_threadsafe.h"
 #include "base/power_monitor/power_observer.h"
+#include "base/synchronization/lock.h"
 
 namespace base {
 
@@ -20,24 +21,35 @@ class PowerMonitorSource;
 class BASE_EXPORT PowerMonitor {
  public:
   // Takes ownership of |source|.
-  explicit PowerMonitor(scoped_ptr<PowerMonitorSource> source);
-  ~PowerMonitor();
+  static void Initialize(scoped_ptr<PowerMonitorSource> source);
+  static void Shutdown();
 
-  // Get the process-wide PowerMonitor (if not present, returns NULL).
-  static PowerMonitor* Get();
+  // Has the PowerMonitor already been initialized?
+  static bool IsInitialized();
 
   // Add and remove an observer.
   // Can be called from any thread.
   // Must not be called from within a notification callback.
-  void AddObserver(PowerObserver* observer);
-  void RemoveObserver(PowerObserver* observer);
+  static bool AddObserver(PowerObserver* observer);
+  static bool RemoveObserver(PowerObserver* observer);
 
   // Is the computer currently on battery power.
-  bool IsOnBatteryPower();
+  static bool IsOnBatteryPower();
 
  private:
+  explicit PowerMonitor(scoped_ptr<PowerMonitorSource> source);
+  ~PowerMonitor();
   friend class PowerMonitorSource;
 
+  static Lock* GetSingletonLock();
+  // Must manually aqcuire the lock before calling
+  static PowerMonitor* GetSingleton();
+
+  void AddObserverImpl(PowerObserver* observer);
+  void RemoveObserverImpl(PowerObserver* observer);
+  // Is the computer currently on battery power.
+  bool IsOnBatteryPowerImpl();
+
   PowerMonitorSource* Source();
 
   void NotifyPowerStateChange(bool battery_in_use);