net doesn't depend on libevent directly now.

net/socket/tcp_client_socket_libevent.cc

 // Copyright (c) 2011 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/socket/tcp_client_socket.h"
 
 #include <errno.h>
 #include <fcntl.h>
 #include <netdb.h>
 #include <sys/socket.h>
 #include <netinet/tcp.h>
 #if defined(OS_POSIX)
 #include <netinet/in.h>
 #endif
 
 #include "base/eintr_wrapper.h"
 #include "base/logging.h"
 #include "base/message_loop.h"
 #include "base/metrics/stats_counters.h"
 #include "base/string_util.h"
 #include "net/base/address_list_net_log_param.h"
 #include "net/base/connection_type_histograms.h"
 #include "net/base/io_buffer.h"
 #include "net/base/ip_endpoint.h"
 #include "net/base/net_errors.h"
 #include "net/base/net_log.h"
 #include "net/base/net_util.h"
 #include "net/base/network_change_notifier.h"
-#if defined(USE_SYSTEM_LIBEVENT)
-#include <event.h>
-#else
-#include "third_party/libevent/event.h"
-#endif
 
 namespace net {
 
 namespace {
 
 const int kInvalidSocket = -1;
 
 // DisableNagle turns off buffering in the kernel. By default, TCP sockets will
 // wait up to 200ms for more data to complete a packet before transmitting.
 // After calling this function, the kernel will not wait. See TCP_NODELAY in
@@ skipping 666 matching lines @@
 
 bool TCPClientSocketLibevent::WasEverUsed() const {
   return use_history_.was_used_to_convey_data();
 }
 
 bool TCPClientSocketLibevent::UsingTCPFastOpen() const {
   return use_tcp_fastopen_;
 }
 
 }  // namespace net