Fix a -Wstring-plus-int warning in (linux-only) flip_server.

net/tools/flip_server/acceptor_thread.cc

 // Copyright (c) 2009 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/tools/flip_server/acceptor_thread.h"
 
 #include <netinet/in.h>
 #include <netinet/tcp.h>  // For TCP_NODELAY
 #include <sys/socket.h>
 #include <sys/types.h>
@@ skipping 71 matching lines @@
 
 void SMAcceptorThread::HandleConnection(int server_fd,
                                         struct sockaddr_in *remote_addr) {
   int on = 1;
   int rc;
   if (acceptor_->disable_nagle_) {
     rc = setsockopt(server_fd, IPPROTO_TCP,  TCP_NODELAY,
                     reinterpret_cast<char*>(&on), sizeof(on));
     if (rc < 0) {
       close(server_fd);
-      LOG(ERROR) << "setsockopt() failed fd=" + server_fd;
+      LOG(ERROR) << "setsockopt() failed fd=" << server_fd;
       return;
     }
   }
 
   SMConnection* server_connection = FindOrMakeNewSMConnection();
   if (server_connection == NULL) {
     VLOG(1) << ACCEPTOR_CLIENT_IDENT << "Acceptor: Closing fd " << server_fd;
     close(server_fd);
     return;
   }
@@ skipping 98 matching lines @@
 }
 
 void SMAcceptorThread::SMConnectionDone(SMConnection* sc) {
   VLOG(1) << ACCEPTOR_CLIENT_IDENT << "Done with connection.";
   tmp_unused_server_connections_.push_back(sc);
 }
 
 }  // namespace net