DCHECK -> CHECK for UDPSocket Read/Write calls when previouse in progress.

net/udp/udp_socket_libevent.cc

 // 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.
 
 #include "net/udp/udp_socket_libevent.h"
 
 #include <errno.h>
 #include <fcntl.h>
 #include <netdb.h>
 #include <net/if.h>
@@ skipping 152 matching lines @@
                             const CompletionCallback& callback) {
   return RecvFrom(buf, buf_len, NULL, callback);
 }
 
 int UDPSocketLibevent::RecvFrom(IOBuffer* buf,
                                 int buf_len,
                                 IPEndPoint* address,
                                 const CompletionCallback& callback) {
   DCHECK(CalledOnValidThread());
   DCHECK_NE(kInvalidSocket, socket_);
-  DCHECK(read_callback_.is_null());
+  CHECK(read_callback_.is_null());

[wtc, 2014/09/24 15:10:07]

Ryan: I think it would be better to add a new net error
code, say ERR_BUSY or ERR_IN_USE, and make these functions
return that error code rather than crashing with a CHECK
failure:

  if (!read_callback_.is_null())
    return ERR_BUSY;

   DCHECK(!recv_from_address_);
   DCHECK(!callback.is_null());  // Synchronous operation not supported
   DCHECK_GT(buf_len, 0);
 
   int nread = InternalRecvFrom(buf, buf_len, address);
   if (nread != ERR_IO_PENDING)
     return nread;
 
   if (!base::MessageLoopForIO::current()->WatchFileDescriptor(
           socket_, true, base::MessageLoopForIO::WATCH_READ,
@@ skipping 23 matching lines @@
                               const CompletionCallback& callback) {
   return SendToOrWrite(buf, buf_len, &address, callback);
 }
 
 int UDPSocketLibevent::SendToOrWrite(IOBuffer* buf,
                                      int buf_len,
                                      const IPEndPoint* address,
                                      const CompletionCallback& callback) {
   DCHECK(CalledOnValidThread());
   DCHECK_NE(kInvalidSocket, socket_);
-  DCHECK(write_callback_.is_null());
+  CHECK(write_callback_.is_null());
   DCHECK(!callback.is_null());  // Synchronous operation not supported
   DCHECK_GT(buf_len, 0);
 
   int result = InternalSendTo(buf, buf_len, address);
   if (result != ERR_IO_PENDING)
     return result;
 
   if (!base::MessageLoopForIO::current()->WatchFileDescriptor(
           socket_, true, base::MessageLoopForIO::WATCH_WRITE,
           &write_socket_watcher_, &write_watcher_)) {
@@ skipping 539 matching lines @@
     return MapSystemError(errno);
 
   return OK;
 }
 
 void UDPSocketLibevent::DetachFromThread() {
   base::NonThreadSafe::DetachFromThread();
 }
 
 }  // namespace net