arc: Handle metrics for Auth operations.

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 4ae0fc1a0f6d2344445d30cee432445739e38446..ad8fc784c27fe890dfa7b07c8c57f31f77bc21da 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -1597,6 +1597,36 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="ArcAuth.CheckinAttempts" units="attempts">
+  <owner>elijahtaylor@chromium.org</owner>
+  <summary>
+    Number of attempts done while waiting for the check-in task to be completed
+    before GMS sign-in. 0 means that device was already checked-in. This is

[Ilya Sherman, 2017/02/23 22:23:22]

Same question about GMS sign-in here, fwiw.

[khmel, 2017/02/23 22:41:37]

Sorry, missed this.

+    recorded in case check-in task is completed successfully.
+  </summary>
+</histogram>
+
+<histogram name="ArcAuth.CheckinTime" units="ms">
+  <owner>elijahtaylor@chromium.org</owner>
+  <summary>
+    Elapsed time waiting for the check-in task to be completed. This is recorded
+    in case check-in task is completed successfully.
+  </summary>
+</histogram>
+
+<histogram name="ArcAuth.NetworkWaitTime" units="ms">
+  <owner>elijahtaylor@chromium.org</owner>
+  <summary>
+    Elapsed time waiting for network connection before starting other
+    authorization operations.
+  </summary>
+</histogram>
+
+<histogram name="ArcAuth.SignInTime" units="ms">
+  <owner>elijahtaylor@chromium.org</owner>
+  <summary>Elapsed time waiting for GMS sign-in completed.</summary>

[Ilya Sherman, 2017/02/23 22:23:22]

nit: s/completed/to complete.

[khmel, 2017/02/23 22:41:37]

Done.

+</histogram>
+
 <histogram name="ArcRuntime.LowMemoryKiller.FreedSize" units="KB">
   <obsolete>
     Renamed to Arc.LowMemoryKiller.FreedSize on 2016/03/24.