Give access to a network time kept in the variation service.

chrome/browser/metrics/variations/variations_service.h

 // Copyright (c) 2012 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_METRICS_VARIATIONS_VARIATIONS_SERVICE_H_
 #define CHROME_BROWSER_METRICS_VARIATIONS_VARIATIONS_SERVICE_H_
 
 #include <string>
 
 #include "base/compiler_specific.h"
@@ skipping 29 matching lines @@
   // Creates field trials based on Variations Seed loaded from local prefs. If
   // there is a problem loading the seed data, all trials specified by the seed
   // may not be created.
   bool CreateTrialsFromSeed(PrefService* local_prefs);
 
   // Calls FetchVariationsSeed once and repeats this periodically. See
   // implementation for details on the period. Must be called after
   // |CreateTrialsFromSeed|.
   void StartRepeatedVariationsSeedFetch();
 
+  // TODO(mad): Remove this once NetworkTimeService is extracted as stand alone.
+  bool GetNetworkTime(base::Time* network_time,
+                      base::TimeDelta* uncertainty) const;
+
 #if defined(OS_WIN)
   // Starts syncing Google Update Variation IDs with the registry.
   void StartGoogleUpdateRegistrySync();
 #endif
 
   // Exposed for testing.
   void SetCreateTrialsFromSeedCalledForTesting(bool called);
 
   // Register Variations related prefs in Local State.
   static void RegisterPrefs(PrefServiceSimple* prefs);
@@ skipping 116 matching lines @@
   base::RepeatingTimer<VariationsService> timer_;
 
   // Helper class used to tell this service if it's allowed to make network
   // resource requests.
   scoped_ptr<ResourceRequestAllowedNotifier> resource_request_allowed_notifier_;
 
   // The start time of the last seed request. This is used to measure the
   // latency of seed requests. Initially zero.
   base::TimeTicks last_request_started_time_;
 
+  // TODO(mad): Eventually move this to a NetworkTimeService.
+  class NetworkTimeService {

[Alexei Svitkine (slow), 2013/02/01 22:18:08]

Put it in a separate file. "Service" is too ambitious a name for this, for now.

How about NetworkTimeTracker?

You can put the separate file in the same directory as VariationsService with a
TODO comment explaining the eventual plan.

[MAD, 2013/02/04 21:07:43]

Done.

+   public:
+    NetworkTimeService() {

[Alexei Svitkine (slow), 2013/02/01 22:18:08]

When this is a file, add a dtor and don't inline their impls.

[MAD, 2013/02/04 21:07:43]

Done.

+    };
+
+    // Returns a network time based on previous url request header value and CPU
+    // ticks count since then. Returns false if no network time is available
+    // yet. Can also return the error range if |uncertainty| isn't NULL.
+    bool GetNetworkTime(base::Time* network_time,
+                        base::TimeDelta* uncertainty) const;
+   private:
+    // TODO(mad): Remove this once NetworkTimeService is extracted from here.
+    friend class VariationsService;

[Alexei Svitkine (slow), 2013/02/01 22:18:08]

Remove this and change the SetNetworkTime() call to UpdateNetworkTime(). You can
make it public, since only VariationsService has access to the instance.

[MAD, 2013/02/04 21:07:43]

Done.

+
+    void SetNetworkTime(const base::Time& network_time,
+                        const base::TimeDelta& latency);
+
+    // Remember the network time based on last url request header value.
+    base::Time network_time_;
+
+    // The estimated ticks count when the date was set on the url request.
+    base::TimeTicks network_time_ticks_;
+
+    // Uncertainty of time based on added inaccuracies of the time is acquired.
+    base::TimeDelta network_time_uncertainty_;
+
+    DISALLOW_COPY_AND_ASSIGN(NetworkTimeService);
+  } network_service_;
+
 #if defined(OS_WIN)
   // Helper that handles synchronizing Variations with the Registry.
   VariationsRegistrySyncer registry_syncer_;
 #endif
 };
 
 }  // namespace chrome_variations
 
 #endif  // CHROME_BROWSER_METRICS_VARIATIONS_VARIATIONS_SERVICE_H_