Add CHECK() in UdpSocketLibevent to debug crbug.com/452121

net/udp/udp_socket_libevent.h

 // 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.
 
 #ifndef NET_UDP_UDP_SOCKET_LIBEVENT_H_
 #define NET_UDP_UDP_SOCKET_LIBEVENT_H_
 
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/message_loop/message_loop.h"
@@ skipping 27 matching lines @@
   // Returns a net error code.
   int Connect(const IPEndPoint& address);
 
   // Binds the address/port for this socket to |address|.  This is generally
   // only used on a server. Should be called after Open().
   // Returns a net error code.
   int Bind(const IPEndPoint& address);
 
   // Closes the socket.
   // TODO(rvargas, hidehiko): Disallow re-Open() after Close().
-  void Close();
+  int Close();
 
   // Copies the remote udp address into |address| and returns a net error code.
   int GetPeerAddress(IPEndPoint* address) const;
 
   // Copies the local udp address into |address| and returns a net error code.
   // (similar to getsockname)
   int GetLocalAddress(IPEndPoint* address) const;
 
   // IO:
   // Multiple outstanding read requests are not supported.
@@ skipping 238 matching lines @@
   CompletionCallback write_callback_;
 
   BoundNetLog net_log_;
 
   DISALLOW_COPY_AND_ASSIGN(UDPSocketLibevent);
 };
 
 }  // namespace net
 
 #endif  // NET_UDP_UDP_SOCKET_LIBEVENT_H_