gfe-relnote: In GFE, export number of QUIC packets written per write operation. Protected by FLAGS_quic_export_server_num_packets_per_write_histogram.

PiperOrigin-RevId: 249251940
Change-Id: Ie92306bb1d10dec11c2801353026b363f3046d81
diff --git a/quic/core/quic_packet_creator.cc b/quic/core/quic_packet_creator.cc
index e69ac85..9f9a68f 100644
--- a/quic/core/quic_packet_creator.cc
+++ b/quic/core/quic_packet_creator.cc
@@ -868,11 +868,7 @@
   } else {
     header->nonce = nullptr;
   }
-  if (!packet_.packet_number.IsInitialized()) {
-    packet_.packet_number = framer_->first_sending_packet_number();
-  } else {
-    ++packet_.packet_number;
-  }
+  packet_.packet_number = NextSendingPacketNumber();
   header->packet_number = packet_.packet_number;
   header->packet_number_length = GetPacketNumberLength();
   header->retry_token_length_length = GetRetryTokenLengthLength();
@@ -1128,5 +1124,12 @@
   return 7;
 }
 
+QuicPacketNumber QuicPacketCreator::NextSendingPacketNumber() const {
+  if (!packet_number().IsInitialized()) {
+    return framer_->first_sending_packet_number();
+  }
+  return packet_number() + 1;
+}
+
 #undef ENDPOINT  // undef for jumbo builds
 }  // namespace quic