Adding histogram to count number of RTTs for handshake when confirmation is required.

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 ce6325a46fa61b12806f60dc300e2f5b404b4a8b..1dc6c24df1087de5244838137b9ced7d496dbed5 100644
--- a/tools/metrics/histograms/histograms.xml
+++ b/tools/metrics/histograms/histograms.xml
@@ -16164,6 +16164,17 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   <summary>The IP Address family of this connection, as seen locally.</summary>
 </histogram>
 
+<histogram name="Net.QuicSession.ConnectRandomPortRequiringConfirmation"
+    units="RTTs">
+  <owner>jri@chromium.org</owner>
+  <summary>
+    Samples of the number of round-trips needed by a QUIC connection before a
+    request could be sent by the client, when handshake confirmation was
+    required. (The operating system randomly selected a source port for the
+    connection.)
+  </summary>
+</histogram>
+
 <histogram name="Net.QuicSession.CreationError" enum="QuicSessionErrorCodes">
   <owner>jar@chromium.org</owner>
   <owner>rch@chromium.org</owner>
@@ -54165,6 +54176,8 @@ To add a new entry, add it with any value and run test to compute valid value.
   <suffix name="ForHTTP" label="Only insecure HTTP connections are counted."/>

[Ryan Hamilton, 2014/08/26 16:50:24]

nit: I notice that the name of this suffix is QuicRttCount but it seems like
something like QuicConnectionType (or some such) would be a better choice?

[Jana, 2014/08/26 17:22:08]

Yeah -- I noticed it too, and now that we've both noticed it, I've changed it
per your suggestion :-)

   <suffix name="ForHTTPS" label="Only secure HTTPS connections are counted."/>
   <affected-histogram name="Net.QuicSession.ConnectRandomPort"/>
+  <affected-histogram
+      name="Net.QuicSession.ConnectRandomPortRequiringConfirmation"/>
   <affected-histogram name="Net.QuicSession.ConnectSelectPort"/>
   <affected-histogram name="Net.QuicSession.HandshakeRoundTrips"/>
 </histogram_suffixes>