SystemMonitor refactoring: move power state monitor into a separate class called 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
new file mode 100644
index 0000000000000000000000000000000000000000..b8e98d9f4efe2e7880408fc7272e653b27b6edc9
--- /dev/null
+++ b/base/power_monitor/power_monitor.h
@@ -0,0 +1,129 @@
+// Copyright (c) 2012 The Chromium Authors. All rights reserved.

[vandebo (ex-Chrome), 2012/10/11 00:58:43]

It'd be nice to have this file tracked as a move.  You can adjust the threshold
for that by adding a -M option in depot_tools/third_party/upload.py:1330
(GenerateDiff)

[Hongbo Min, 2012/10/11 07:57:53]

Done. git cl upload have an option "--similarity" to do the same thing. I set
the similarity to 10. 

+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_POWER_MONITOR_POWER_MONITOR_H_
+#define BASE_POWER_MONITOR_POWER_MONITOR_H_
+
+#include "base/base_export.h"
+#include "base/basictypes.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"

[vandebo (ex-Chrome), 2012/10/11 00:58:43]

Move this to line 10

[Hongbo Min, 2012/10/11 07:57:53]

Done.

+#if defined(ENABLE_BATTERY_MONITORING)
+#include "base/timer.h"
+#endif  // defined(ENABLE_BATTERY_MONITORING)
+
+#if defined(OS_IOS)
+#include <objc/runtime.h>
+#endif  // OS_IOS
+
+namespace base {
+
+class BASE_EXPORT PowerMonitor {
+ public:
+  // 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.
+  };
+
+  PowerMonitor();
+  ~PowerMonitor();
+
+  // Callbacks will be called on the thread which creates the SystemMonitor.

[vandebo (ex-Chrome), 2012/10/11 00:58:43]

SystemMonitor -> PowerMonitor

[Hongbo Min, 2012/10/11 07:57:53]

Done.

+  // 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 BASE_EXPORT PowerObserver {

[vandebo (ex-Chrome), 2012/10/11 00:58:43]

per willchan's comment, move this to the top of the class with the other type
definitions.

[Hongbo Min, 2012/10/11 07:57:53]

Done.

+   public:
+    // Notification of a change in power status of the computer, such
+    // as from switching between battery and A/C power.
+    virtual void OnPowerStateChange(bool on_battery_power) {}
+
+    // Notification that the system is suspending.
+    virtual void OnSuspend() {}
+
+    // Notification that the system is resuming.
+    virtual void OnResume() {}
+
+   protected:
+    virtual ~PowerObserver() {}
+  };
+
+  void AddPowerObserver(PowerObserver* observer);

[vandebo (ex-Chrome), 2012/10/11 00:58:43]

Add a copy of the comment from system_monitor.h:151 here.

[Hongbo Min, 2012/10/11 07:57:53]

Done.

+  void RemovePowerObserver(PowerObserver* observer);
+
+  // 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_;
+  }
+
+  // Return the single instance in the application wide.
+  static PowerMonitor* Get();

[vandebo (ex-Chrome), 2012/10/11 00:58:43]

We should use Singleton instead of the custom Get method.

[Hongbo Min, 2012/10/11 07:57:53]

Done.

+
+#if defined(OS_MACOSX)

[vandebo (ex-Chrome), 2012/10/11 00:58:43]

Move these init type methods to just below the con/destructor.

[Hongbo Min, 2012/10/11 07:57:53]

Done.

+  // Allocate system resources needed by the PowerMonitor class.
+  //
+  // This function must be called before instantiating an instance of the class
+  // and before the Sandbox is initialized.
+#if !defined(OS_IOS)
+  static void AllocateSystemIOPorts();
+#else
+  static void AllocateSystemIOPorts() {}
+#endif  // OS_IOS
+#endif  // OS_MACOSX
+
+ private:
+  friend class HWNDMessageHandler;

[vandebo (ex-Chrome), 2012/10/11 00:58:43]

Looks like the Mac implementation needs a friend function declaration as well

[Hongbo Min, 2012/10/11 07:57:53]

If making a friend function for Mac, it will introduce additional type
dependency in power_monitor.h, and lots of places also need to access
ProcessPowerMessage, so I just keep the original methods instead of renaming to
HandlePowerEvent and making it private in this CL.

[vandebo (ex-Chrome), 2012/10/11 20:49:57]

Part of the point of refactoring is to remove/make private the ProcessFoo
methods.  I don't think a friend declaration here would introduce new type
dependencies. 

[vandebo (ex-Chrome), 2012/10/12 00:15:51]

If need be, you can create another function that mirrors the ProcessFoo
arguments within the Mac file in order to avoid forward declaring other types.

+  friend class PowerMonitorTest_PowerNotifications_Test;
+
+#if defined(OS_MACOSX)
+  void PlatformInit();
+  void PlatformDestroy();
+#endif
+
+  // Handle the power event and notify its observers with the specific state.
+  void HandlePowerEvent(PowerEvent event_id);
+
+  // 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();
+
+  void NotifyPowerStateChange();
+  void NotifySuspend();
+  void NotifyResume();
+
+#if defined(OS_IOS)
+  // Holds pointers to system event notification observers.
+  std::vector<id> notification_observers_;
+#endif
+
+#if defined(ENABLE_BATTERY_MONITORING)
+    base::OneShotTimer<PowerMonitor> delayed_battery_check_;
+#endif
+  scoped_refptr<ObserverListThreadSafe<PowerObserver> > power_observer_list_;

[vandebo (ex-Chrome), 2012/10/11 00:58:43]

power_observer_list_ -> observers_

[Hongbo Min, 2012/10/11 07:57:53]

Done.

+  bool battery_in_use_;
+  bool suspended_;
+
+  DISALLOW_COPY_AND_ASSIGN(PowerMonitor);
+};
+
+}  // namespace base
+
+#endif  // BASE_POWER_MONITOR_POWER_MONITOR_H_