net doesn't depend on libevent directly now.

net/socket/tcp_client_socket_libevent.h

 // 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.
 
 #ifndef NET_SOCKET_TCP_CLIENT_SOCKET_LIBEVENT_H_
 #define NET_SOCKET_TCP_CLIENT_SOCKET_LIBEVENT_H_
 #pragma once
 
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/message_loop.h"
 #include "base/threading/non_thread_safe.h"
 #include "net/base/address_list.h"
 #include "net/base/completion_callback.h"
 #include "net/base/net_log.h"
 #include "net/socket/stream_socket.h"
 
-struct event;  // From libevent
-
 namespace net {
 
 class BoundNetLog;
 
 // A client socket that uses TCP as the transport layer.
 class TCPClientSocketLibevent : public StreamSocket, base::NonThreadSafe {
  public:
   // The IP address(es) and port number to connect to.  The TCP socket will try
   // each IP address in the list until it succeeds in establishing a
   // connection.
@@ skipping 166 matching lines @@
 
   // True when TCP FastOpen is in use and we have done the connect.
   bool tcp_fastopen_connected_;
 
   DISALLOW_COPY_AND_ASSIGN(TCPClientSocketLibevent);
 };
 
 }  // namespace net
 
 #endif  // NET_SOCKET_TCP_CLIENT_SOCKET_LIBEVENT_H_