Merge NetworkTimeNotifier to NetworkTimeTracker

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/callback.h"
-#include "base/memory/weak_ptr.h"
+#include "base/memory/scoped_ptr.h"
 #include "base/threading/thread_checker.h"
 #include "base/time/time.h"
-#include "net/base/network_time_notifier.h"
 
-class IOThread;
-class NetworkTimeTrackerTest;
+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, but may live
-// on any thread.
-// Note that all NetworkTimeTracker instances interact with a
-// NetworkTimeNotifier singleton that lives on the IO thread. This class
-// enables arbitrary threads to maintain their own network time source without
-// having to deal with the details of the Notifier's implementation.
+// for a corresponding local time. This class is not thread safe.
 class NetworkTimeTracker {
  public:
-  // Callback for updating network time based on http responses. This callback
-  // is thread safe and should be called directly without posting to any thread.
-  // The parameters are:
-  // const base::Time& network_time - the actual time.
-  // const base::TimeDelta& resolution - how precise the reading is.
-  // const base::TimeDelta& latency - the http request's latency.
-  typedef base::Callback<void(const base::Time&,
-                              const base::TimeDelta&,
-                              const base::TimeDelta&)> UpdateCallback;
-
-  NetworkTimeTracker();
+  explicit NetworkTimeTracker(scoped_ptr<base::TickClock> tick_clock);
   ~NetworkTimeTracker();
 
-  // Starts tracking network time.
-  void Start();
-
   struct TimeMapping {
-    TimeMapping(base::Time local_time, base::Time network_time);
+    TimeMapping(const base::Time& local_time, const base::Time& network_time);
     base::Time local_time;
     base::Time network_time;
   };
 
   // Initializes from saved times to be able to compute network time before
   // receiving accurate time from HTTP response.
   void InitFromSavedTime(const TimeMapping& saved);
 
   // 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(const base::TimeTicks& time_ticks,
                       base::Time* network_time,
                       base::TimeDelta* uncertainty) const;
 
-  // Build a callback for use in updating the network time notifier.
-  // This method must be called on the UI thread, while the callback can be
-  // called from any thread.
-  static UpdateCallback BuildNotifierUpdateCallback();
+  // 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(const base::Time& network_time,
+                         const base::TimeDelta& resolution,
+                         const base::TimeDelta& latency,
+                         const base::TimeTicks& post_time);
 
   bool received_network_time() const {
     return received_network_time_;
   }
 
  private:
-  friend class NetworkTimeTrackerTest;
-
-  // Returns the callback used to register for time updates from the network
-  // time notifier on the IO thread.
-  net::NetworkTimeNotifier::ObserverCallback BuildObserverCallback();
-
-  // net::NetworkTimeNotifier::ObserverCallback implementation.
-  void OnNetworkTimeUpdate(
-      const base::Time& network_time,
-      const base::TimeTicks& network_time_ticks,
-      const base::TimeDelta& network_time_uncertainty);
+  // For querying current time ticks.
+  scoped_ptr<base::TickClock> tick_clock_;
 
   // Network time based on last call to UpdateNetworkTime().
   base::Time network_time_;
 
-  // The estimated ticks count from when |network_time_| was set based on the
-  // system's tick count.
+  // 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::WeakPtrFactory<NetworkTimeTracker> weak_ptr_factory_;
-
   base::ThreadChecker thread_checker_;
 
   bool received_network_time_;
 
   DISALLOW_COPY_AND_ASSIGN(NetworkTimeTracker);
 };
 
 #endif  // CHROME_BROWSER_NETWORK_TIME_NETWORK_TIME_TRACKER_H_