Add varz to track QUIC packets and bytes sent by transmission type.

net/quic/quic_connection.cc

Index: net/quic/quic_connection.cc
diff --git a/net/quic/quic_connection.cc b/net/quic/quic_connection.cc
index 8ae91ef80abe8ab7f06e25ed9cd836055d192a2c..dce0ca15c8305b7a53e9828d7bc98723bf864c6a 100644
--- a/net/quic/quic_connection.cc
+++ b/net/quic/quic_connection.cc
@@ -1300,8 +1300,11 @@ bool QuicConnection::WritePacket(QueuedPacket packet) {
   }
   if (debug_visitor_) {
     // Pass the write result to the visitor.
-    debug_visitor_->OnPacketSent(
-        sequence_number, packet.encryption_level, *encrypted, result);
+    debug_visitor_->OnPacketSent(sequence_number,
+                                 packet.encryption_level,
+                                 packet.transmission_type,
+                                 *encrypted,
+                                 result);
   }
   if (result.status == WRITE_STATUS_BLOCKED) {
     visitor_->OnWriteBlocked();