Log serial read and write errors on Windows.

device/serial/serial_io_handler_win.cc

 // Copyright 2014 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 <windows.h>
 
 #include "device/serial/serial_io_handler_win.h"
 
 namespace device {
 
@@ skipping 193 matching lines @@
   DCHECK(CalledOnValidThread());
   DCHECK(pending_write_buffer());
   DCHECK(file().IsValid());
 
   BOOL ok = ::WriteFile(file().GetPlatformFile(),
                         pending_write_buffer(),
                         pending_write_buffer_len(),
                         NULL,
                         &write_context_->overlapped);
   if (!ok && GetLastError() != ERROR_IO_PENDING) {
+    VPLOG(1) << "Write failed";
     QueueWriteCompleted(0, serial::SEND_ERROR_SYSTEM_ERROR);
   }
 }
 
 void SerialIoHandlerWin::CancelReadImpl() {
   DCHECK(CalledOnValidThread());
   DCHECK(file().IsValid());
   ::CancelIo(file().GetPlatformFile());
 }
 
@@ skipping 70 matching lines @@
       ReadCompleted(bytes_transferred, read_cancel_reason());
     } else if (error != ERROR_SUCCESS && error != ERROR_OPERATION_ABORTED) {
       ReadCompleted(0, serial::RECEIVE_ERROR_SYSTEM_ERROR);
     } else if (pending_read_buffer()) {
       BOOL ok = ::ReadFile(file().GetPlatformFile(),
                            pending_read_buffer(),
                            pending_read_buffer_len(),
                            NULL,
                            &read_context_->overlapped);
       if (!ok && GetLastError() != ERROR_IO_PENDING) {
+        VPLOG(1) << "Read failed";
         ReadCompleted(0, serial::RECEIVE_ERROR_SYSTEM_ERROR);
       }
     }
   } else if (context == read_context_) {
     if (read_canceled()) {
       ReadCompleted(bytes_transferred, read_cancel_reason());
     } else if (error != ERROR_SUCCESS && error != ERROR_OPERATION_ABORTED) {
       ReadCompleted(0, serial::RECEIVE_ERROR_SYSTEM_ERROR);
     } else {
       ReadCompleted(bytes_transferred,
@@ skipping 78 matching lines @@
 std::string SerialIoHandler::MaybeFixUpPortName(const std::string& port_name) {
   // For COM numbers less than 9, CreateFile is called with a string such as
   // "COM1". For numbers greater than 9, a prefix of "\\\\.\\" must be added.
   if (port_name.length() > std::string("COM9").length())
     return std::string("\\\\.\\").append(port_name);
 
   return port_name;
 }
 
 }  // namespace device