Add code count for packets dropped by blocked port

PiperOrigin-RevId: 405535871

quic/core/quic_dispatcher.cc

diff --git a/quic/core/quic_dispatcher.cc b/quic/core/quic_dispatcher.cc
index 61f79dd..2d3a260 100644
--- a/quic/core/quic_dispatcher.cc
+++ b/quic/core/quic_dispatcher.cc
@@ -544,6 +544,7 @@
     const ReceivedPacketInfo& packet_info) {
   if (IsSourceUdpPortBlocked(packet_info.peer_address.port())) {
     // Silently drop the received packet.
+    QUIC_CODE_COUNT(quic_dropped_blocked_port);
     return true;
   }