Add histograms for tracking the number of client hellos send. This will let us understand how frequ…

tools/metrics/histograms/histograms.xml

 <!--
 Copyright 2013 The Chromium Authors. All rights reserved.
 Use of this source code is governed by a BSD-style license that can be
 found in the LICENSE file.
 -->
 
 <!--
 This file is used to generate a comprehensive list of Chrome histograms along
 with a detailed description for each histogram.
 
@@ skipping 3647 matching lines @@
 </histogram>
 
 <histogram name="Net.PublicKeyPinSuccess" enum="BooleanSuccess">
   <summary>
     A validated certificate chain may be subject to additional
     &quot;pinning&quot; requirements on a per-domain basis. This records the
     fraction of successful matches between a certificate chain and a pin list.
   </summary>
 </histogram>
 
+<histogram name="Net.QuicCryptoHandshakeConfirmed">
+  <summary>
+    True if the QUIC crypto handshake was confirmed by the server.
+  </summary>
+</histogram>
+
+<histogram name="Net.QuicCryptoHandshakeConfirmedNumSentClientHellos">
+  <summary>
+    The number of client hello messages sent when the crypto handshake was
+    confirmed.
+  </summary>
+</histogram>
+
+<histogram name="Net.QuicEncryptionEstablished">
+  <summary>True if the QUIC crypto handshake established encryption.</summary>
+</histogram>
+
+<histogram name="Net.QuicNumSentClientHellos">
+  <summary>The number of client hello messages sent.</summary>
+</histogram>
+
 <histogram name="Net.RenegotiationExtensionSupported">
   <summary>
     True if the HTTP request was sent to a server which supports the TLS
     renegotiation extension.
   </summary>
 </histogram>
 
 <histogram name="Net.SocketIdleTimeBeforeNextUse_ReusedSocket">
   <summary>The time an already used socket sat idle before being used.</summary>
 </histogram>
@@ skipping 12151 matching lines @@
 <fieldtrial name="SSLResumption">
   <group name="Resume_Handshake" label="Session Resumption"/>
   <group name="Full_Handshake" label="Full"/>
   <affected-histogram name="Net.SSL_Connection_Latency"/>
   <affected-histogram name="Net.SSL_Connection_Latency_Google"/>
 </fieldtrial>
 
 </fieldtrials>
 
 </histogram-configuration>