Refine NetworkTimeTracker histograms

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 44 matching lines @@
   // Describes the result of a GetNetworkTime() call, describing whether
   // network time was available and if not, why not.
   enum NetworkTimeResult {
     // Network time is available.
     NETWORK_TIME_AVAILABLE,
     // A time has been retrieved from the network in the past, but
     // network time is no longer available because the tracker fell out
     // of sync due to, for example, a suspend/resume.
     NETWORK_TIME_SYNC_LOST,
     // Network time is unavailable because the tracker has not yet
-    // retrieved a time from the network.
-    NETWORK_TIME_NO_SYNC,
+    // attempted to retrieve a time from the network.
+    NETWORK_TIME_NO_SYNC_ATTEMPT,
+    // Network time is unavailable because the tracker has not yet
+    // successfully retrieved a time from the network (at least one
+    // attempt has been made but all have failed).
+    NETWORK_TIME_NO_SUCCESSFUL_SYNC,
+    // Network time is unavailable because the tracker has not yet
+    // attempted to retrieve a time from the network, but the first
+    // attempt is currently pending.
+    NETWORK_TIME_FIRST_SYNC_PENDING,
+    // Network time is unavailable because the tracker has made failed
+    // attempts to retrieve a time from the network, but an attempt is
+    // currently pending.
+    NETWORK_TIME_SUBSEQUENT_SYNC_PENDING,
   };
 
   static void RegisterPrefs(PrefRegistrySimple* registry);
 
   // Constructor.  Arguments may be stubbed out for tests.  |getter|, if not
   // null, will cause automatic queries to a time server.  Otherwise, time is
   // available only if |UpdateNetworkTime| is called.
   NetworkTimeTracker(std::unique_ptr<base::Clock> clock,
                      std::unique_ptr<base::TickClock> tick_clock,
                      PrefService* pref_service,
@@ skipping 91 matching lines @@
   // latency time.  See UpdateNetworkTime(...) implementation for details.  The
   // tick clock is the one actually used to return values to callers, but both
   // clocks must agree to within some tolerance.
   base::Time time_at_last_measurement_;
   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 a time query has failed (either a network error, a non-200

[mab, 2016/10/14 06:35:01]

like true if any time query has failed ever?

[estark, 2016/10/14 07:23:46]

In this object's lifetime, yeah. It's just used to distinguish whether we've
made any attempts or not when we have no sync. And come to think of it,
|time_query_completed_| is probably a more natural way to track it. Changed to
that.

+  // HTTP status code, or a bad response, such as a bad signature or
+  // malformed data).
+  bool time_query_failed_;
+
   base::ThreadChecker thread_checker_;
 
   DISALLOW_COPY_AND_ASSIGN(NetworkTimeTracker);
 };
 
 }  // namespace network_time
 
 #endif  // COMPONENTS_NETWORK_TIME_NETWORK_TIME_TRACKER_H_