Add histogram to track NPN/ALPN.

net/socket/ssl_client_socket_pool.cc

Index: net/socket/ssl_client_socket_pool.cc
diff --git a/net/socket/ssl_client_socket_pool.cc b/net/socket/ssl_client_socket_pool.cc
index 6356783144b28986d9a2cbcdc8468a67d40b9fb5..a866b6c9513ef41eeec32145e6526ebcd28dd2aa 100644
--- a/net/socket/ssl_client_socket_pool.cc
+++ b/net/socket/ssl_client_socket_pool.cc
@@ -452,8 +452,10 @@ int SSLConnectJob::DoSSLConnectComplete(int result) {
   // GetNextProto will fail and and trigger a NOTREACHED if we pass in a socket
   // that hasn't had SSL_ImportFD called on it. If we get a certificate error
   // here, then we know that we called SSL_ImportFD.
-  if (result == OK || IsCertificateError(result))
+  if (result == OK || IsCertificateError(result)) {
     status = ssl_socket_->GetNextProto(&proto);
+    ssl_socket_->RecordNegotiationExtension();
+  }
 
   // If we want spdy over npn, make sure it succeeded.
   if (status == SSLClientSocket::kNextProtoNegotiated) {