Removing file_thread_task_runner parameter from SerialIoHandler

device/serial/serial_io_handler_posix.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_POSIX_H_
 #define DEVICE_SERIAL_SERIAL_IO_HANDLER_POSIX_H_
 
 #include <memory>
 
 #include "base/files/file_descriptor_watcher_posix.h"
@@ skipping 29 matching lines @@
                         int buffer_len,
                         int bytes_read,
                         bool& break_detected,
                         bool& parity_error_detected);
 
  private:
   friend class SerialIoHandler;
   friend class SerialIoHandlerPosixTest;
 
   SerialIoHandlerPosix(
-      scoped_refptr<base::SingleThreadTaskRunner> file_thread_task_runner,
       scoped_refptr<base::SingleThreadTaskRunner> ui_thread_task_runner);
   ~SerialIoHandlerPosix() override;
 
   void AttemptRead(bool within_read);
   void RunReadCompleted(bool within_read,
                         int bytes_read,
                         serial::ReceiveError error);
 
   // Called when file() is writable without blocking.
   void OnFileCanWriteWithoutBlocking();
 
   void EnsureWatchingReads();
   void EnsureWatchingWrites();
 
   std::unique_ptr<base::FileDescriptorWatcher::Controller> file_read_watcher_;
   std::unique_ptr<base::FileDescriptorWatcher::Controller> file_write_watcher_;
 
   ErrorDetectState error_detect_state_;
   bool parity_check_enabled_;
   char chars_stashed_[2];
   int num_chars_stashed_;
 
   DISALLOW_COPY_AND_ASSIGN(SerialIoHandlerPosix);
 };
 
 }  // namespace device
 
 #endif  // DEVICE_SERIAL_SERIAL_IO_HANDLER_POSIX_H_