Record latencies of connection and arrival of first message in UMA

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 d472046d3fcdc09c8e1ace30f56c1b13ace8eb28..5982c296ba739d17b9d06a9d5eedaf226f11363b 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -8194,6 +8194,14 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   <summary>Net error results from GCM connection attempts.</summary>
 </histogram>
 
+<histogram name="GCM.ConnectionLatency">
+  <owner>juyik@chromium.org</owner>
+  <summary>
+    The time between the initiation of a connection and the successful
+    completion of it.
+  </summary>
+</histogram>
+
 <histogram name="GCM.ConnectionResetReason" enum="GCMConnectionResetReason">
   <owner>zea@chromium.org</owner>
   <summary>Reasons for GCM connection resets.</summary>
@@ -8215,6 +8223,21 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </summary>
 </histogram>
 
+<histogram name="GCM.DataMessageBurstReceivedInterval">
+  <owner>juyik@chromium.org</owner>
+  <summary>
+    Interval between two successive received data message bursts.
+  </summary>
+</histogram>
+
+<histogram name="GCM.FirstReceivedDataMessageLatencyAfterConnection">
+  <owner>juyik@chromium.org</owner>
+  <summary>
+    The time between the successful completion of the connection and the arrival
+    of the first data message.
+  </summary>
+</histogram>
+
 <histogram name="GCM.LoadSucceeded" enum="BooleanSuccess">
   <owner>zea@chromium.org</owner>
   <summary>
@@ -8249,6 +8272,18 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </summary>
 </histogram>
 
+<histogram name="GCM.ReceivedDataMessageBurstSize">
+  <owner>juyik@chromium.org</owner>
+  <summary>Number of messages in a received GCM data message burst.</summary>
+</histogram>
+
+<histogram name="GCM.ReceivedDataMessageIntervalWithinBurstMs">
+  <owner>juyik@chromium.org</owner>
+  <summary>
+    Interval between messages within a received GCM data message burst.
+  </summary>
+</histogram>
+
 <histogram name="GCM.RegistrationCompleteTime" units="milliseconds">

[jar (doing other things), 2014/08/01 04:41:46]

nit: You should follow this pattern, and have a "units" tag as shown here in
each case where you are not using an enum or such.

[juyik, 2014/08/01 19:01:05]

Done.

   <owner>jianli@chromium.org</owner>
   <summary>