Adding an option for peers to negotiate the length of the QUIC

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 a0794f33cff6fb959fbfe272d814d3a0fb74e002..f9c2e207a4dcfa12ce047f4471cb33e66971948d 100644
--- a/net/quic/quic_connection.cc
+++ b/net/quic/quic_connection.cc
@@ -270,6 +270,11 @@ void QuicConnection::SetFromConfig(const QuicConfig& config) {
     SetIdleNetworkTimeout(config.IdleConnectionStateLifetime());
   }
   sent_packet_manager_.SetFromConfig(config);
+  if (FLAGS_allow_truncated_connection_ids_for_quic &&
+      config.HasReceivedBytesForConnectionId()) {
+    packet_generator_.SetConnectionIdLength(
+        config.ReceivedBytesForConnectionId());
+  }
   max_undecryptable_packets_ = config.max_undecryptable_packets();
 }