Created multi-process-friendly PowerMonitor interface.

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 fc3df48a7349287bb1cde00946c183aa590158ae..c876c9c9c067ddd78bf160a93a93e1b5c0973714 100644
--- a/base/power_monitor/power_monitor.h
+++ b/base/power_monitor/power_monitor.h
@@ -11,132 +11,44 @@
 #include "base/observer_list_threadsafe.h"
 #include "base/power_monitor/power_observer.h"
 
-#if defined(OS_WIN)
-#include <windows.h>
-
-// Windows HiRes timers drain the battery faster so we need to know the battery
-// status.  This isn't true for other platforms.
-#define ENABLE_BATTERY_MONITORING 1
-#else
-#undef ENABLE_BATTERY_MONITORING
-#endif  // !OS_WIN
-
-#if defined(ENABLE_BATTERY_MONITORING)
-#include "base/timer/timer.h"
-#endif  // defined(ENABLE_BATTERY_MONITORING)
-
-#if defined(OS_IOS)
-#include <objc/runtime.h>
-#endif  // OS_IOS
-
 namespace base {
 
+class PowerMonitorSource;
+
 // A class used to monitor the power state change and notify the observers about
 // the change event.
 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.
-  };
-
+  // The default constructor should only be used in the browser process. All
+  // other processes should explicitly pass an appropriate PowerMonitorSource

[palmer, 2013/07/09 21:16:10]

Is there any way to enforce that, with e.g. a DCHECK on process type? (Maybe you
do, I haven't checked the implementation yet.)

[vandebo (ex-Chrome), 2013/07/09 22:22:08]

This should be a short lived comment.  A follow up CL should update other uses
of PowerMonitor and remove this constructor.

   PowerMonitor();
+  // PowerMonitor assumes ownership of source

[palmer, 2013/07/09 21:16:10]

Nit: I'd rewrite this comment as:

    Takes ownership of |source|.

+  explicit PowerMonitor(PowerMonitorSource* source);
   ~PowerMonitor();
 
-  // Get the application-wide PowerMonitor (if not present, returns NULL).
+  // Get the process-wide PowerMonitor (if not present, returns NULL).
   static PowerMonitor* Get();
 
-#if defined(OS_MACOSX)
-  // 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
-
   // 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);
 
-  // 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_;
-  }
-
- private:
-  friend class PowerMonitorTest;
-  // A friend function that is allowed to access the private ProcessPowerEvent.
-  friend void ProcessPowerEventHelper(PowerEvent);
+  PowerMonitorSource* Source();

[vandebo (ex-Chrome), 2013/07/09 22:22:08]

Is Source() just needed for the device source implementations?  It's ugly to
expose it.  This might be uglier, but we could hide it by having protected:
static PowerMonitorSource::Source() and private: PowerMonitor:Source().  The
existing friend declarations should then let ProcessPowerEventHelper() get
Source().

Actually even easier than that would be to make ProcessPowerEvent() be private
static.  Internally it can do the PowerMonitor::Get()

 
-#if defined(OS_WIN)
-  // Represents a message-only window for power message handling on Windows.
-  // Only allow PowerMonitor to create it.
-  class PowerMessageWindow {
-   public:
-    PowerMessageWindow();
-    ~PowerMessageWindow();
+  // Is the computer currently on battery power.

[palmer, 2013/07/09 21:16:10]

While you're here, give this a more boolean-sounding name, e.g.
|IsOnBatteryPower|.

+  bool BatteryPower();
 
-   private:
-    void ProcessWmPowerBroadcastMessage(int event_id);
-    LRESULT CALLBACK WndProc(HWND hwnd, UINT message,
-                             WPARAM wparam, LPARAM lparam);
-    static LRESULT CALLBACK WndProcThunk(HWND hwnd,
-                                         UINT message,
-                                         WPARAM wparam,
-                                         LPARAM lparam);
-    // Instance of the module containing the window procedure.
-    HMODULE instance_;
-    // A hidden message-only window.
-    HWND message_hwnd_;
-  };
-#endif  // OS_WIN
-
-#if defined(OS_MACOSX)
-  void PlatformInit();
-  void PlatformDestroy();
-#endif
-
-  // Cross-platform handling of a power event.
-  void ProcessPowerEvent(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();
+ private:
+  friend class PowerMonitorSource;
 
-  void NotifyPowerStateChange();
+  void NotifyPowerStateChange(bool battery_in_use);
   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> > observers_;
-  bool battery_in_use_;
-  bool suspended_;
-
-#if defined(OS_WIN)
-  PowerMessageWindow power_message_window_;
-#endif
+  scoped_ptr<PowerMonitorSource> source_;
 
   DISALLOW_COPY_AND_ASSIGN(PowerMonitor);
 };