Earlier check for nullptr.

net/quic/quic_connection.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "net/quic/quic_connection.h"
 
 #include <string.h>
 #include <sys/types.h>
 
 #include <algorithm>
@@ skipping 1968 matching lines @@
   packet_generator_.AddControlFrame(QuicFrame(frame));
   packet_generator_.FlushAllQueuedFrames();
 }
 
 void QuicConnection::CloseConnection(QuicErrorCode error, bool from_peer) {
   if (!connected_) {
     DVLOG(1) << "Connection is already closed.";
     return;
   }
   connected_ = false;
+  DCHECK(visitor_ != nullptr);
+  visitor_->OnConnectionClosed(error, from_peer);
   if (debug_visitor_ != nullptr) {
     debug_visitor_->OnConnectionClosed(error, from_peer);
   }
-  DCHECK(visitor_ != nullptr);
-  visitor_->OnConnectionClosed(error, from_peer);
   // Cancel the alarms so they don't trigger any action now that the
   // connection is closed.
   ack_alarm_->Cancel();
   ping_alarm_->Cancel();
   fec_alarm_->Cancel();
   resume_writes_alarm_->Cancel();
   retransmission_alarm_->Cancel();
   send_alarm_->Cancel();
   timeout_alarm_->Cancel();
   mtu_discovery_alarm_->Cancel();
@@ skipping 340 matching lines @@
       packet_number_of_last_sent_packet_ + packets_between_mtu_probes_ + 1;
   ++mtu_probe_count_;
 
   DVLOG(2) << "Sending a path MTU discovery packet #" << mtu_probe_count_;
   SendMtuDiscoveryPacket(mtu_discovery_target_);
 
   DCHECK(!mtu_discovery_alarm_->IsSet());
 }
 
 }  // namespace net