Battery listener for download service in native code.

components/download/internal/scheduler/battery_listener.h

+// Copyright 2017 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 COMPONENTS_DOWNLOAD_INTERNAL_SCHEDULER_BATTERY_LISTENER_H_
+#define COMPONENTS_DOWNLOAD_INTERNAL_SCHEDULER_BATTERY_LISTENER_H_
+
+#include <memory>
+
+#include "base/observer_list.h"
+#include "base/power_monitor/power_observer.h"
+#include "components/download/public/download_params.h"
+
+namespace download {
+
+// Listen to battery charing state changes and notify observers in download
+// service.
+// TODO(xingliu): Converts to device service when it's fully done.
+class BatteryListener : public base::PowerObserver {
+ public:
+  class Observer {
+   public:
+    // Called when certain battery requirements are meet.
+    virtual void OnBatteryChange(
+        SchedulingParams::BatteryRequirements battery_status) = 0;
+  };
+
+  BatteryListener();
+  ~BatteryListener() override;
+
+  // Retrieves the current minimum battery requirement.
+  SchedulingParams::BatteryRequirements CurrentBatteryStatus() const;
+
+  // Start to listen to battery change.
+  void Start();
+
+  // Stop to listen to battery change.
+  void Stop();
+
+  // Adds/Removes observers.
+  void AddObserver(Observer* observer);
+  void RemoveObserver(Observer* observer);
+
+ private:
+  // base::PowerObserver implementation.
+  void OnPowerStateChange(bool on_battery_power) override;
+
+  // Notifies |observers_| about battery requirement change.
+  void NotifyBatteryChange(SchedulingParams::BatteryRequirements);
+
+  // Observers to monitor battery change in download service.
+  base::ObserverList<Observer> observers_;
+
+  DISALLOW_COPY_AND_ASSIGN(BatteryListener);
+};
+
+}  // namespace download
+
+#endif  // COMPONENTS_DOWNLOAD_INTERNAL_SCHEDULER_BATTERY_LISTENER_H_