[chromeos] New PowerManagerClient observer to collect power data.

chromeos/power/power_data_collector.h

+// Copyright (c) 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 CHROMEOS_POWER_POWER_DATA_COLLECTOR_H_
+#define CHROMEOS_POWER_POWER_DATA_COLLECTOR_H_
+
+#include <vector>
+
+#include "base/basictypes.h"
+#include "base/compiler_specific.h"
+#include "base/gtest_prod_util.h"
+#include "base/time/time.h"
+#include "chromeos/dbus/power_manager_client.h"
+
+namespace power_manager {
+class PowerSupplyProperties;
+}
+
+namespace chromeos {
+
+// A class which starts collecting power metrics, like the battery charge, as
+// soon as it is initialized via Initialize().
+//
+// This class is implemented as a global singleton, initialized after
+// DBusThreadManager which it depends on.
+class PowerDataCollector : public PowerManagerClient::Observer {
+ public:
+  struct PowerSupplySnapshot {
+    PowerSupplySnapshot();
+
+    // Time when the snapshot was captured.
+    base::TimeTicks time;
+
+    // True if connected to external power at the time of the snapshot.
+    bool external_power;
+
+    // The battery charge as a percentage of full charge in range [0.0, 100.00].
+    double battery_percent;
+  };
+
+  const std::vector<PowerSupplySnapshot>& power_supply_data() const {
+    return power_supply_data_;
+  }
+
+  // Can be called only after DBusThreadManager is initialized.
+  static void Initialize();
+
+  // Can be called only if initialized via Initialize, and before
+  // DBusThreadManager is destroyed.
+  static void Shutdown();
+
+  // Returns the global instance of PowerDataCollector.
+  static PowerDataCollector* Get();
+
+ private:
+  friend class PowerDataCollectorTest;
+  FRIEND_TEST_ALL_PREFIXES(PowerDataCollectorTest, PowerChanged);
+
+  PowerDataCollector();
+
+  virtual ~PowerDataCollector();
+
+  // PowerManagerClient::Observer implementation:
+  virtual void PowerChanged(

[Daniel Erat, 2013/12/13 23:57:09]

if you make this public, then you can get rid of the friend stuff above and
remove the gtest_prod_util.h include, right?

[Siva Chandra, 2013/12/14 00:35:50]

Yes. But are you telling me to remove?

I felt it appropriate to keep the overriden method to be private as it is not
supposed to be called by the "clients".

[Daniel Erat, 2013/12/14 01:00:30]

your call. in general, i've seen FRIEND_TEST_ALL_PREFIXES() often lead to a lot
of duplicated testing code that touches a class's internals, making it painful
to change the implementation later. i think that the risk of anyone thinking
it's a good idea to call a public PowerChanged() method from anywhere besides
PowerManagerClient is awfully slim.

+      const power_manager::PowerSupplyProperties& prop) OVERRIDE;
+
+ private:

[Daniel Erat, 2013/12/13 23:57:09]

remove this extra 'private' label

[Siva Chandra, 2013/12/14 00:35:50]

Done.

+  std::vector<PowerSupplySnapshot> power_supply_data_;
+
+  DISALLOW_COPY_AND_ASSIGN(PowerDataCollector);
+};
+
+}  // namespace chromeos
+
+#endif  // CHROMEOS_POWER_POWER_DATA_COLLECTOR_H_