QUIC - Added histogram to track how often chrome sends/receives

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 8f9951027fcfab529a91aba50711e21071db6ccc..76fb234bf4196ad097d1571b6d42829f1ffd31c7 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -17232,6 +17232,22 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   </summary>
 </histogram>
 
+<histogram name="Net.QuicSession.BlockedFramesReceived">

[Alexei Svitkine (slow), 2014/10/22 15:30:45]

Nit: One suggestion:

Name these with Net.QuicSession.BlockedFrames.Received and
Net.QuicSession.BlockedFrames.Sent, so you get grouping on the dashboard.

Both here and in the code.

[ramant (doing other things), 2014/10/22 16:54:46]

Done.

+  <owner>rtenneti@chromium.org</owner>
+  <summary>
+    The number of BLOCKED frames recevied by a QuicSession when the session is
+    closed.
+  </summary>
+</histogram>
+
+<histogram name="Net.QuicSession.BlockedFramesSent">
+  <owner>rtenneti@chromium.org</owner>
+  <summary>
+    The number of BLOCKED frames sent by a QuicSession when the session is
+    closed.
+  </summary>
+</histogram>
+
 <histogram name="Net.QuicSession.ClosedDuringInitializeSession">
   <owner>rch@chromium.org</owner>
   <summary>