Refine NetworkTimeTracker histograms

components/network_time/network_time_tracker.h

Index: components/network_time/network_time_tracker.h
diff --git a/components/network_time/network_time_tracker.h b/components/network_time/network_time_tracker.h
index ae1f26820721cd6d77daa4f80c8baa776eef7581..0c00f75837f3c4d0006d468d64bd219c53e4c6e1 100644
--- a/components/network_time/network_time_tracker.h
+++ b/components/network_time/network_time_tracker.h
@@ -62,8 +62,20 @@ class NetworkTimeTracker : public net::URLFetcherDelegate {
     // 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);
@@ -175,6 +187,11 @@ class NetworkTimeTracker : public net::URLFetcherDelegate {
   // 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);