Record packet drop reason when header protection failed

This was missing due to an oversight and is causing our
Chrome metrics to be wrong for Q050.

Stats-only change, not flag protected

PiperOrigin-RevId: 310244491
Change-Id: I92b5836fcf9e7f4fb56ea840151c5d9e4c000a7e

quic/core/quic_framer.cc

diff --git a/quic/core/quic_framer.cc b/quic/core/quic_framer.cc
index 30a3742..b05b457 100644
--- a/quic/core/quic_framer.cc
+++ b/quic/core/quic_framer.cc
@@ -1737,6 +1737,7 @@
         visitor_->OnUndecryptablePacket(
             QuicEncryptedPacket(encrypted_reader->FullPayload()),
             decryption_level, has_decryption_key);
+        RecordDroppedPacketReason(DroppedPacketReason::DECRYPTION_FAILURE);
         set_detailed_error(quiche::QuicheStrCat(
             "Unable to decrypt ", EncryptionLevelToString(decryption_level),
             " header protection", has_decryption_key ? "" : " (missing key)",