Log error code for write errors in QuicConnection.

net/quic/core/quic_connection.cc

Index: net/quic/core/quic_connection.cc
diff --git a/net/quic/core/quic_connection.cc b/net/quic/core/quic_connection.cc
index 734740cf849bdbb5d704c240fe8d5a5d5441326c..1286e1b35921c599884ff1a2e992dd992d887a7b 100644
--- a/net/quic/core/quic_connection.cc
+++ b/net/quic/core/quic_connection.cc
@@ -1744,7 +1744,8 @@ bool QuicConnection::WritePacket(SerializedPacket* packet) {
                 << " from host " << (self_address().address().empty()
                                          ? " empty address "
                                          : self_address().ToStringWithoutPort())
-                << " to address " << peer_address().ToString();
+                << " to address " << peer_address().ToString()
+                << " with error code " << result.error_code;
     return false;
   }