Componentize chrome/browser/network_time

chrome/browser/network_time/network_time_tracker.h

-// Copyright 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 CHROME_BROWSER_NETWORK_TIME_NETWORK_TIME_TRACKER_H_
-#define CHROME_BROWSER_NETWORK_TIME_NETWORK_TIME_TRACKER_H_
-
-#include "base/memory/scoped_ptr.h"
-#include "base/threading/thread_checker.h"
-#include "base/time/time.h"
-
-class PrefRegistrySimple;
-class PrefService;
-
-namespace base {
-class TickClock;
-}
-
-// A class that receives network time updates and can provide the network time
-// for a corresponding local time. This class is not thread safe.
-class NetworkTimeTracker {
- public:
-  static void RegisterPrefs(PrefRegistrySimple* registry);
-
-  NetworkTimeTracker(scoped_ptr<base::TickClock> tick_clock,
-                     PrefService* pref_service);
-  ~NetworkTimeTracker();
-
-  // Returns the network time corresponding to |time_ticks| if network time
-  // is available. Returns false if no network time is available yet. Can also
-  // return the error range if |uncertainty| isn't NULL.
-  bool GetNetworkTime(base::TimeTicks time_ticks,
-                      base::Time* network_time,
-                      base::TimeDelta* uncertainty) const;
-
-  // Calculates corresponding time ticks according to the given parameters.
-  // The provided |network_time| is precise at the given |resolution| and
-  // represent the time between now and up to |latency| + (now - |post_time|)
-  // ago.
-  void UpdateNetworkTime(base::Time network_time,
-                         base::TimeDelta resolution,
-                         base::TimeDelta latency,
-                         base::TimeTicks post_time);
-
-  bool received_network_time() const {
-    return received_network_time_;
-  }
-
- private:
-  // For querying current time ticks.
-  scoped_ptr<base::TickClock> tick_clock_;
-
-  PrefService* pref_service_;
-
-  // Network time based on last call to UpdateNetworkTime().
-  base::Time network_time_;
-
-  // The estimated local time from |tick_clock| that corresponds with
-  // |network_time|. Assumes the actual network time measurement was performed
-  // midway through the latency time, and does not account for suspect/resume
-  // events since the network time was measured.
-  // See UpdateNetworkTime(..) implementation for details.
-  base::TimeTicks network_time_ticks_;
-
-  // Uncertainty of |network_time_| based on added inaccuracies/resolution.
-  // See UpdateNetworkTime(..) implementation for details.
-  base::TimeDelta network_time_uncertainty_;
-
-  base::ThreadChecker thread_checker_;
-
-  bool received_network_time_;
-
-  DISALLOW_COPY_AND_ASSIGN(NetworkTimeTracker);
-};
-
-#endif  // CHROME_BROWSER_NETWORK_TIME_NETWORK_TIME_TRACKER_H_