Measure time between secure time queries

components/network_time/network_time_tracker.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 COMPONENTS_NETWORK_TIME_NETWORK_TIME_TRACKER_H_
 #define COMPONENTS_NETWORK_TIME_NETWORK_TIME_TRACKER_H_
 
 #include <stdint.h>
 #include <memory>
 
@@ skipping 199 matching lines @@
   base::TimeTicks ticks_at_last_measurement_;
 
   // Uncertainty of |network_time_| based on added inaccuracies/resolution.  See
   // UpdateNetworkTime(...) implementation for details.
   base::TimeDelta network_time_uncertainty_;
 
   // True if any time query has completed (but not necessarily succeeded) in
   // this NetworkTimeTracker's lifetime.
   bool time_query_completed_;
 
+  // The time that was received from the last network time fetch made by
+  // CheckTime(). Unlike |network_time_at_least_measurement_|, this time
+  // is not updated when UpdateNetworkTime() is called. Used for UMA
+  // metrics.
+  base::Time last_fetched_time_;
+
   // Callbacks to run when the in-progress time fetch completes.
   std::vector<base::Closure> fetch_completion_callbacks_;
 
   base::ThreadChecker thread_checker_;
 
   DISALLOW_COPY_AND_ASSIGN(NetworkTimeTracker);
 };
 
 }  // namespace network_time
 
 #endif  // COMPONENTS_NETWORK_TIME_NETWORK_TIME_TRACKER_H_