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..16ef21e7d927ac46651a95bcd5b98989bf24cf1a 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -1597,6 +1597,33 @@ http://cs/file:chrome/histograms.xml - but prefer this file for new entries.
   </summary>
 </histogram>
 
+<histogram name="ArcAuth.CheckinAttempts" units="attempts">
+  <owner>elijahtaylor@google.com</owner>

[Ilya Sherman, 2017/02/23 21:23:35]

Can you use an @chromium.org address here?  Also, I noticed that Elijah isn't on
the review list for this CL.  Are you sure that he is comfortable with being
signed up to own these?

[khmel, 2017/02/23 21:57:45]

I changed to @chromium.org (however in many other existing we use @google.com
for ARC). Yes, we discussed what need to be done with Elijah. He is also in cc
list.

+  <summary>
+    Number of attempts did while waiting for checkin task completed before GMS

[Ilya Sherman, 2017/02/23 21:23:34]

nit: s/did/done

[Ilya Sherman, 2017/02/23 21:23:34]

nit: s/checkin task completed/the check-in task to be completed

[khmel, 2017/02/23 21:57:45]

Done.

[khmel, 2017/02/23 21:57:45]

Done.

+    sign-in. 0 means that device was already checked-in prior to GMS sign-in.

[Ilya Sherman, 2017/02/23 21:23:35]

Please document when this is recorded -- on success?  After each attempt? 
Something else?

[khmel, 2017/02/23 21:57:45]

Done.

+  </summary>
+</histogram>
+
+<histogram name="ArcAuth.CheckinTime" units="ms">
+  <owner>elijahtaylor@google.com</owner>
+  <summary>
+    Elapsed time waiting for checkin task completed before GMS sign-in.

[Ilya Sherman, 2017/02/23 21:23:35]

Same grammatical tweak suggestions as above.  Also, I'm not quite sure what
"before GMS sign-in" means, in this sentence.  Is the intent to convey that the
checkin task runs at multiple times, and this histogram is only recorded for
checkin tasks that run before GMS sign-in?  That complete before GMS sign-in? 
Something else?  Please reword this to clarify, if you can.

[khmel, 2017/02/23 21:57:45]

I removed mentioning GMS sign-in. It is actually not required.

+  </summary>
+</histogram>
+
+<histogram name="ArcAuth.NetworkWaitTime" units="ms">
+  <owner>elijahtaylor@google.com</owner>
+  <summary>
+    Elapsed time waiting for network connection before GMS sign-in.
+  </summary>
+</histogram>
+
+<histogram name="ArcAuth.SignInTime" units="ms">
+  <owner>elijahtaylor@google.com</owner>
+  <summary>Elapsed time waiting for GMS sign-in completed.</summary>
+</histogram>
+
 <histogram name="ArcRuntime.LowMemoryKiller.FreedSize" units="KB">
   <obsolete>
     Renamed to Arc.LowMemoryKiller.FreedSize on 2016/03/24.