Chrome power profiler service

content/public/browser/power_profiler_service.h

+// Copyright 2014 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_PUBLIC_BROWSER_POWER_PROFILER_SERVICE_H_
+#define CONTENT_PUBLIC_BROWSER_POWER_PROFILER_SERVICE_H_
+
+#include <set>
+
+#include "base/basictypes.h"
+#include "base/memory/singleton.h"
+#include "base/observer_list.h"
+#include "base/task_runner.h"
+#include "base/timer/timer.h"
+#include "content/common/content_export.h"
+#include "content/public/browser/power_data_provider.h"
+#include "content/public/browser/power_profiler_observer.h"
+
+namespace content {
+
+// a class used to monitor the power usage and tell profiler the power data.
+class CONTENT_EXPORT PowerProfilerService {
+ public:
+  static PowerProfilerService* GetInstance();
+
+  // Add and remove an observer.
+  bool AddObserver(PowerProfilerObserver* observer);
+  void RemoveObserver(PowerProfilerObserver* observer);
+  void UpdateResolution();

[qsr, 2014/01/23 12:50:06]

Why is this method public? My guess is that it is for the case where an observer
would need to change its resolution? As this is not needed yet, just put this in
the private section. When it is needed, I think removing the observer and
re-adding it would be better than exposing those kind of internal details.

[Pan, 2014/01/25 09:35:53]

right, done

+
+  bool IsAvailable();
+
+ private:
+  enum Status {
+    UNINITIALIZED, // Unitialized.
+    INITIALIZED, // Initialized, not in profiling.
+    PROFILING, // In profiling.
+  };
+
+  friend struct DefaultSingletonTraits<PowerProfilerService>;
+
+  PowerProfilerService();

[qsr, 2014/01/23 12:50:06]

You probably want a second constructor that takes a PowerDataProvider (maybe
private), so that you can test this class.

 And following this could you also write a test for this class.

[Pan, 2014/01/25 09:35:53]

thanks for your help, unit test is prepared, please review.

+  virtual ~PowerProfilerService() {}
+
+  void Start();
+  void Stop();
+
+  void OnTimer();
+  void InitializeDelays();
+
+  // ProcessData is delegated to thread in WorkerPool.
+  void ProcessData();
+
+  // Notify works in UI thread.
+  void Notify(const PowerEvent&);
+
+  base::RepeatingTimer<PowerProfilerService> query_power_timer_;
+  scoped_refptr<base::TaskRunner> task_runner_;
+
+  base::TimeDelta delay_;
+  base::TimeDelta delays_[PowerProfilerObserver::TYPE_COUNT]; // kinds of delay.
+  Status status_;
+  ObserverList<PowerProfilerObserver> observers_;
+
+  scoped_ptr<PowerDataProvider> data_provider_;
+
+  DISALLOW_COPY_AND_ASSIGN(PowerProfilerService);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_PUBLIC_BROWSER_POWER_PROFILER_SERVICE_H_