Record UMA statistics for file_stream operations.

net/base/net_errors_win.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/base/net_errors.h"
 
 #include <winsock2.h>
 
 #include "base/logging.h"
 
 namespace net {
 
 // Map winsock and system errors to Chromium errors.
 Error MapSystemError(int os_error) {
+  if (os_error != 0)
+    DVLOG(2) << "Error " << os_error;
+
   // There are numerous Winsock error codes, but these are the ones we thus far
   // find interesting.
   switch (os_error) {
     case WSAEWOULDBLOCK:
       return ERR_IO_PENDING;
     case WSAEACCES:
       return ERR_ACCESS_DENIED;
     case WSAENETDOWN:
       return ERR_INTERNET_DISCONNECTED;
     case WSAETIMEDOUT:
@@ skipping 83 matching lines @@
     case ERROR_SUCCESS:
       return OK;
     default:
       LOG(WARNING) << "Unknown error " << os_error
                    << " mapped to net::ERR_FAILED";
       return ERR_FAILED;
   }
 }
 
 }  // namespace net