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

net/udp/udp_client_socket.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_UDP_CLIENT_SOCKET_H_
 #define NET_SOCKET_UDP_CLIENT_SOCKET_H_
 
 #include "net/base/net_log.h"
 #include "net/base/rand_callback.h"
 #include "net/udp/datagram_client_socket.h"
@@ skipping 13 matching lines @@
   ~UDPClientSocket() override;
 
   // DatagramClientSocket implementation.
   int Connect(const IPEndPoint& address) override;
   int Read(IOBuffer* buf,
            int buf_len,
            const CompletionCallback& callback) override;
   int Write(IOBuffer* buf,
             int buf_len,
             const CompletionCallback& callback) override;
-  void Close() override;
+  int Close() override;
   int GetPeerAddress(IPEndPoint* address) const override;
   int GetLocalAddress(IPEndPoint* address) const override;
   int SetReceiveBufferSize(int32 size) override;
   int SetSendBufferSize(int32 size) override;
   const BoundNetLog& NetLog() const override;
 
 #if defined(OS_WIN)
   // Switch to use non-blocking IO. Must be called right after construction and
   // before other calls.
   void UseNonBlockingIO();
 #endif
 
  private:
   UDPSocket socket_;
   DISALLOW_COPY_AND_ASSIGN(UDPClientSocket);
 };
 
 }  // namespace net
 
 #endif  // NET_SOCKET_UDP_CLIENT_SOCKET_H_