Removing file_thread_task_runner parameter from SerialIoHandler

device/serial/serial_io_handler_win.cc

Index: device/serial/serial_io_handler_win.cc
diff --git a/device/serial/serial_io_handler_win.cc b/device/serial/serial_io_handler_win.cc
index 75461fe7843c22e6657f1e92efd17667b69d6726..9a25e9a69bbb1ff7f8104188fd0b88a385fa26d4 100644
--- a/device/serial/serial_io_handler_win.cc
+++ b/device/serial/serial_io_handler_win.cc
@@ -151,9 +151,8 @@ bool GetCOMPort(const std::string friendly_name, std::string* com_port) {
 
 // static
 scoped_refptr<SerialIoHandler> SerialIoHandler::Create(
-    scoped_refptr<base::SingleThreadTaskRunner> file_thread_task_runner,
     scoped_refptr<base::SingleThreadTaskRunner> ui_thread_task_runner) {
-  return new SerialIoHandlerWin(file_thread_task_runner, ui_thread_task_runner);
+  return new SerialIoHandlerWin(ui_thread_task_runner);
 }
 
 class SerialIoHandlerWin::UiThreadHelper final
@@ -359,9 +358,8 @@ bool SerialIoHandlerWin::ConfigurePortImpl() {
 }
 
 SerialIoHandlerWin::SerialIoHandlerWin(
-    scoped_refptr<base::SingleThreadTaskRunner> file_thread_task_runner,
     scoped_refptr<base::SingleThreadTaskRunner> ui_thread_task_runner)
-    : SerialIoHandler(file_thread_task_runner, ui_thread_task_runner),
+    : SerialIoHandler(ui_thread_task_runner),
       event_mask_(0),
       is_comm_pending_(false),
       helper_(nullptr),