[BackgroundSync Cleanup] Remove power observer

content/browser/background_sync/background_sync_power_observer.h

-// Copyright 2015 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 CONTENT_BROWSER_BACKGROUND_SYNC_BACKGROUND_SYNC_POWER_OBSERVER_H_
-#define CONTENT_BROWSER_BACKGROUND_SYNC_BACKGROUND_SYNC_POWER_OBSERVER_H_
-
-#include "base/bind.h"
-#include "base/macros.h"
-#include "base/power_monitor/power_observer.h"
-#include "content/browser/background_sync/background_sync.pb.h"
-#include "content/common/content_export.h"
-
-namespace content {
-
-// BackgroundSyncPowerObserver monitors the charging status of the device and
-// determines if the power conditions of BackgroundSyncRegistrations are met.
-class CONTENT_EXPORT BackgroundSyncPowerObserver : public base::PowerObserver {
- public:
-  // Creates a BackgroundSyncPowerObserver. |power_callback| is run when the
-  // battery states changes asynchronously via PostMessage.
-  explicit BackgroundSyncPowerObserver(const base::Closure& power_callback);
-
-  ~BackgroundSyncPowerObserver() override;
-
-  // Returns true if the state of the battery (charging or not) meets the needs
-  // of |power_state|.
-  bool PowerSufficient(SyncPowerState power_state) const;
-
- private:
-  friend class BackgroundSyncPowerObserverTest;
-
-  // PowerObserver overrides
-  void OnPowerStateChange(bool on_battery_power) override;
-
-  // |observing_power_monitor_| is true when the constructor is able to find and
-  // register an observer with the base::PowerMonitor. This should always be
-  // true except for tests in which the browser initialization isn't done.
-  bool observing_power_monitor_;
-
-  bool on_battery_;
-
-  // The callback to run when the battery state changes.
-  base::Closure power_changed_callback_;
-
-  DISALLOW_COPY_AND_ASSIGN(BackgroundSyncPowerObserver);
-};
-
-}  // namespace content
-
-#endif  // CONTENT_BROWSER_BACKGROUND_SYNC_BACKGROUND_SYNC_POWER_OBSERVER_H_