Created multi-process-friendly PowerMonitor interface.

base/power_monitor/power_monitor_source.h

Index: base/power_monitor/power_monitor_source.h
diff --git a/base/power_monitor/power_monitor_source.h b/base/power_monitor/power_monitor_source.h
new file mode 100644
index 0000000000000000000000000000000000000000..44cf8d2c6518ebec14a5af11823ccc96ed753fcd
--- /dev/null
+++ b/base/power_monitor/power_monitor_source.h
@@ -0,0 +1,56 @@
+// Copyright 2013 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_POWER_MONITOR_POWER_MONITOR_SOURCE_H_
+#define BASE_POWER_MONITOR_POWER_MONITOR_SOURCE_H_
+
+#include "base/base_export.h"
+#include "base/basictypes.h"
+#include "base/memory/ref_counted.h"
+#include "base/observer_list_threadsafe.h"
+#include "base/synchronization/lock.h"
+
+namespace base {
+
+class PowerMonitor;
+
+// Communicates power state changes to the power monitor.
+class BASE_EXPORT PowerMonitorSource {
+ public:
+  PowerMonitorSource();
+  virtual ~PowerMonitorSource();
+
+  // 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.
+  };
+
+  // Is the computer currently on battery power. Can be called on any thread.
+  bool BatteryPower();

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

Same here: harmonize this name. Why do you have this public and then also the
protected |IsBatteryPower|?

[bajones, 2013/07/09 22:28:00]

Better naming could clear this up. (This was in place before this CL, simply in
a different file)

the public |BatteryPower| is (now) threadsafe and returns the cached battery
state. |IsBatteryPowered| actually queries the hardware's current battery
status, which is probably assumed to be a slow operation and thus is only done
when necessary.

How about |IsOnBatteryPower| for the public call and |QueryBatteryPowerState|
for the protected? 

+
+ protected:
+  friend class PowerMonitorTest;
+
+  // Friend function that is allowed to access the protected ProcessPowerEvent.
+  friend void ProcessPowerEventHelper(PowerEvent);
+
+  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.
+  virtual bool IsBatteryPower();

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

Make this pure virtual ?

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

Maybe IsBatteryPowerImpl() ?

+
+  bool battery_in_use_;

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

Shouldn't these all be private?

+  bool suspended_;
+
+  Lock lock_;
+
+  DISALLOW_COPY_AND_ASSIGN(PowerMonitorSource);
+};
+
+}  // namespace base
+
+#endif  // BASE_POWER_MONITOR_POWER_MONITOR_SOURCE_H_