Deprecate --quic_include_path_id_in_iv.

net/quic/crypto/aead_base_encrypter_openssl.cc

Index: net/quic/crypto/aead_base_encrypter_openssl.cc
diff --git a/net/quic/crypto/aead_base_encrypter_openssl.cc b/net/quic/crypto/aead_base_encrypter_openssl.cc
index 699c60ad934b0d787c0bdc2465ffa3d5bc80e00f..92856a6c0709eea2ee60075a81e5b2595202581f 100644
--- a/net/quic/crypto/aead_base_encrypter_openssl.cc
+++ b/net/quic/crypto/aead_base_encrypter_openssl.cc
@@ -120,15 +120,10 @@ bool AeadBaseEncrypter::EncryptPacket(QuicPathId path_id,
   const size_t nonce_size = nonce_prefix_size_ + sizeof(packet_number);
   ALIGNAS(4) char nonce_buffer[kMaxNonceSize];
   memcpy(nonce_buffer, nonce_prefix_, nonce_prefix_size_);
-  if (FLAGS_quic_include_path_id_in_iv) {
-    uint64_t path_id_packet_number =
-        QuicUtils::PackPathIdAndPacketNumber(path_id, packet_number);
-    memcpy(nonce_buffer + nonce_prefix_size_, &path_id_packet_number,
-           sizeof(path_id_packet_number));
-  } else {
-    memcpy(nonce_buffer + nonce_prefix_size_, &packet_number,
-           sizeof(packet_number));
-  }
+  uint64_t path_id_packet_number =
+      QuicUtils::PackPathIdAndPacketNumber(path_id, packet_number);
+  memcpy(nonce_buffer + nonce_prefix_size_, &path_id_packet_number,
+         sizeof(path_id_packet_number));
 
   if (!Encrypt(StringPiece(nonce_buffer, nonce_size), associated_data,
                plaintext, reinterpret_cast<unsigned char*>(output))) {