Removing file_thread_task_runner parameter from SerialIoHandler

device/serial/serial_io_handler_win.h

 // 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.
 
 #ifndef DEVICE_SERIAL_SERIAL_IO_HANDLER_WIN_H_
 #define DEVICE_SERIAL_SERIAL_IO_HANDLER_WIN_H_
 
 #include <memory>
 
 #include "base/macros.h"
@@ skipping 20 matching lines @@
   serial::ConnectionInfoPtr GetPortInfo() const override;
   bool SetBreak() override;
   bool ClearBreak() override;
   bool PostOpen() override;
 
  private:
   class UiThreadHelper;
   friend class SerialIoHandler;
 
   explicit SerialIoHandlerWin(
-      scoped_refptr<base::SingleThreadTaskRunner> file_thread_task_runner,
       scoped_refptr<base::SingleThreadTaskRunner> ui_thread_task_runner);
   ~SerialIoHandlerWin() override;
 
   // base::MessageLoopForIO::IOHandler implementation.
   void OnIOCompleted(base::MessageLoopForIO::IOContext* context,
                      DWORD bytes_transfered,
                      DWORD error) override;
 
   void OnDeviceRemoved(const std::string& device_path);
 
@@ skipping 18 matching lines @@
   // handler that owns it.
   UiThreadHelper* helper_;
   base::WeakPtrFactory<SerialIoHandlerWin> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(SerialIoHandlerWin);
 };
 
 }  // namespace device
 
 #endif  // DEVICE_SERIAL_SERIAL_IO_HANDLER_WIN_H_