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..eb8471c77eb20931c42f7342787b89bf7f6ed87f
--- /dev/null
+++ b/base/power_monitor/power_monitor_source.h
@@ -0,0 +1,57 @@
+// 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"
+
+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.

[vandebo (ex-Chrome), 2013/06/26 21:40:33]

nit: comment indent; and below.

+  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() const {
+    // Using a lock here is not necessary for just a bool.
+    return battery_in_use_;
+  }
+
+  void ProcessPowerEvent(PowerEvent event_id);

[vandebo (ex-Chrome), 2013/06/26 21:40:33]

Since PowerMonitor::Source() is public, this has to be private or protected.

[bajones, 2013/06/26 22:37:22]

I'm happy to do this, but I'd like to understand why a bit better. This sounds
like layering policy that I'm just not familiar with yet.

[vandebo (ex-Chrome), 2013/06/26 22:50:12]

One bug/flaw in previous versions of SystemMonitr/PowerMonitor was that anyone
could call ProcessFooEvent.  That was determined to be bad because then anyone
could jump in and trigger the Foo event.  Same thing here.  I admit the chain is
weaker because of the IPC, etc - someone could inject a message at any one of
those steps - but it should be clear that they shouldn't do that and I think it
is except for this case.

+
+ protected:
+  friend class PowerMonitor;
+
+  void SetMonitor(PowerMonitor* monitor);

[vandebo (ex-Chrome), 2013/06/26 21:40:33]

Do you need this method, or can it just use PowerMonitor::Get() ?

+
+  // 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();
+
+  PowerMonitor* monitor_;
+  bool battery_in_use_;
+  bool suspended_;
+
+  DISALLOW_COPY_AND_ASSIGN(PowerMonitorSource);
+};
+
+}  // namespace base
+
+#endif  // BASE_POWER_MONITOR_POWER_MONITOR_SOURCE_H_