Reland Chrome power profiler service

content/browser/power_profiler/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_BROWSER_POWER_PROFILER_POWER_PROFILER_SERVICE_H_
+#define CONTENT_BROWSER_POWER_PROFILER_POWER_PROFILER_SERVICE_H_
+
+#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/browser/power_profiler/power_data_provider.h"
+#include "content/browser/power_profiler/power_profiler_observer.h"
+#include "content/common/content_export.h"
+
+namespace content {
+
+// A class used to query power information and notify the observers.
+class CONTENT_EXPORT PowerProfilerService {
+ public:
+  static PowerProfilerService* GetInstance();
+
+  // Add and remove an observer.
+  void AddObserver(PowerProfilerObserver* observer);
+  void RemoveObserver(PowerProfilerObserver* observer);
+
+  bool IsAvailable();
+
+  virtual ~PowerProfilerService();
+
+ private:
+  enum Status {
+    UNINITIALIZED,
+    INITIALIZED,  // Initialized, profiling has not started.
+    PROFILING
+  };
+
+  friend struct DefaultSingletonTraits<PowerProfilerService>;
+  friend class PowerProfilerServiceTest;
+
+  PowerProfilerService();
+
+  PowerProfilerService(scoped_ptr<PowerDataProvider> provider,
+                       scoped_refptr<base::TaskRunner> task_runner,
+                       const base::TimeDelta& sample_period);
+
+  void Start();
+  void Stop();
+
+  // Query power data from PowerDataProvider, executes on the WorkerPool thread.
+  void QueryDataOnTaskRunner();
+
+  // Initiate the query on the UI thread, the task is delegated to
+  // QueryDataOnTaskRunner.
+  void QueryData();
+
+  // Executes on the UI thread.
+  void Notify(const PowerEventVector&);
+
+  base::RepeatingTimer<PowerProfilerService> query_power_timer_;
+  scoped_refptr<base::TaskRunner> task_runner_;
+
+  Status status_;
+
+  // Sampling period of power data measurement.
+  const base::TimeDelta sample_period_;
+  ObserverList<PowerProfilerObserver> observers_;
+
+  scoped_ptr<PowerDataProvider> data_provider_;
+
+  DISALLOW_COPY_AND_ASSIGN(PowerProfilerService);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_POWER_PROFILER_POWER_PROFILER_SERVICE_H_