Disable battery power detection on POSIX since we don't currently use it.

base/system_monitor.h

Index: base/system_monitor.h
diff --git a/base/system_monitor.h b/base/system_monitor.h
index cfcb08a8a85020cc8da4a1b4e224bc94f098c7a3..e2487512f21f55fcaa87da345922133ad3589ba1 100644
--- a/base/system_monitor.h
+++ b/base/system_monitor.h
@@ -1,118 +1,130 @@
-// 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 "base/observer_list_threadsafe.h"
-#include "base/singleton.h"
-
-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();
-  }
-
-  // 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.
-  static void Start();
-
-  //
-  // Power-related APIs
-  //
-
-  // Is the computer currently on battery power.
-  // Can be called on any thread.
-  bool BatteryPower() { 
-    // Using a lock here is not necessary for just a bool.
-    return battery_in_use_;
-  }
-
-  // Normalized list of power events.
-  enum PowerEvent {
-    POWER_STATE_EVENT,  // The Power status of the system has changed.
-    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:
-    // 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;
-  };
-
-  // Add a new observer.
-  // Can be called from any thread.
-  // Must not be called from within a notification callback.
-  void AddObserver(PowerObserver* obs);
-
-  // Remove an existing observer.
-  // Can be called from any thread.
-  // Must not be called from within a notification callback.
-  void RemoveObserver(PowerObserver* obs);
-
-#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_;
-
-  base::OneShotTimer<SystemMonitor> delayed_battery_check_;
-
-  DISALLOW_COPY_AND_ASSIGN(SystemMonitor);
-};
-
-}
-
-#endif  // 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 "base/observer_list_threadsafe.h"
+#include "base/singleton.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
+
+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();
+  }
+
+  // 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() {
+    // Using a lock here is not necessary for just a bool.
+    return battery_in_use_;
+  }
+
+  // Normalized list of power events.
+  enum PowerEvent {
+    POWER_STATE_EVENT,  // The Power status of the system has changed.
+    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:
+    // 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;
+  };
+
+  // Add a new observer.
+  // Can be called from any thread.
+  // Must not be called from within a notification callback.
+  void AddObserver(PowerObserver* obs);
+
+  // Remove an existing observer.
+  // Can be called from any thread.
+  // Must not be called from within a notification callback.
+  void RemoveObserver(PowerObserver* obs);
+
+#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_
+