Refine NetworkTimeTracker histograms

tools/metrics/histograms/histograms.xml

Index: tools/metrics/histograms/histograms.xml
diff --git a/tools/metrics/histograms/histograms.xml b/tools/metrics/histograms/histograms.xml
index 0dac945791abbcefbc46477fce7c2daf49f56031..88347c7929b1e15e31392d044fbf640233709488 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -36736,6 +36736,15 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="NetworkTimeTracker.TimeQueryLatency" units="ms">
+  <owner>estark@chromium.org</owner>
+  <owner>mab@chromium.org</owner>
+  <summary>
+    NetworkTimeTracker makes periodic queries to obtain a secure timestamp over
+    the network. This histogram records the latency of each time query.
+  </summary>
+</histogram>
+
 <histogram name="NetworkTimeTracker.UpdateTimeFetchAttempted">
   <obsolete>
     Deprecated 08/2016 because it does not provide additional information beyond
@@ -91574,7 +91583,7 @@ value.
   <int value="0"
       label="NETWORK_CLOCK_STATE_UNKNOWN_NO_SYNC: accuracy of system clock is
              unknown because there is no information available from the
-             network about what time it is"/>
+             network about what time it is (OBSOLETE)"/>
   <int value="1"
       label="NETWORK_CLOCK_STATE_UNKNOWN_SYNC_LOST: system clock is unknown
              because the system clock has fallen out of sync with the network
@@ -91588,6 +91597,23 @@ value.
   <int value="4"
       label="NETWORK_CLOCK_STATE_CLOCK_IN_FUTURE: system clock is in the
              future relative to network time"/>
+  <int value="5"
+      label="NETWORK_CLOCK_STATE_UNKNOWN_NO_SYNC_ATTEMPT: accuracy of system
+             clock is unknown because there has not yet been any attempt to
+             query the network clock"/>
+  <int value="6"
+      label="NETWORK_CLOCK_STATE_UNKNOWN_NO_SUCCESSFUL_SYNC: accuracy of
+             system clock is unknown because one or more attempts to sync
+             with the network clock have failed"/>
+  <int value="7"
+      label="NETWORK_CLOCK_STATE_UNKNOWN_FIRST_SYNC_PENDING: accuracy of
+             system clock is unknown because the first attempt to sync with
+             the network clock is pending"/>
+  <int value="8"
+      label="NETWORK_CLOCK_STATE_UNKNOWN_SUBSEQUENT_SYNC_PENDING: accuracy of
+             system clock is unknown because one or more attempts to sync
+             with the network clock have failed, and a subsequent attempt is
+             pending"/>
 </enum>
 
 <enum name="NetworkConnectionIPType" type="int">