Log the freshness of the Variations seed in a histogram.

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 146 matching lines @@
   // there is a problem with loading, the pref value is cleared and false is
   // returned. If successful, |seed| will contain the loaded data and true is
   // returned.
   bool LoadTrialsSeedFromPref(PrefService* local_prefs, TrialsSeed* seed);
 
   // Creates and registers a field trial from the |study| data. Disables the
   // trial if IsStudyExpired(study, reference_date) is true.
   void CreateTrialFromStudy(const Study& study,
                             const base::Time& reference_date);
 
+  // Record the time of the most recent successful fetch.
+  void RecordLastFetchTime();
+
   // The pref service used to store persist the variations seed.
   PrefService* local_state_;
 
   // Contains the current seed request. Will only have a value while a request
   // is pending, and will be reset by |OnURLFetchComplete|.
   scoped_ptr<net::URLFetcher> pending_seed_request_;
 
   // The URL to use for querying the Variations server.
   GURL variations_server_url_;
 
@@ skipping 22 matching lines @@
 
 #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_