Revert of Add code to deal with serial device disconnection detection on Windows

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 "base/memory/scoped_ptr.h"
 #include "base/message_loop/message_loop.h"
 #include "base/single_thread_task_runner.h"
@@ skipping 14 matching lines @@
   bool Flush() const override;
   serial::DeviceControlSignalsPtr GetControlSignals() const override;
   bool SetControlSignals(
       const serial::HostControlSignals& control_signals) override;
   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);
-
   // Context used for asynchronous WaitCommEvent calls.
   scoped_ptr<base::MessageLoopForIO::IOContext> comm_context_;
 
   // Context used for overlapped reads.
   scoped_ptr<base::MessageLoopForIO::IOContext> read_context_;
 
   // Context used for overlapped writes.
   scoped_ptr<base::MessageLoopForIO::IOContext> write_context_;
 
   // Asynchronous event mask state
   DWORD event_mask_;
 
   // Indicates if a pending read is waiting on initial data arrival via
   // WaitCommEvent, as opposed to waiting on actual ReadFile completion
   // after a corresponding WaitCommEvent has completed.
   bool is_comm_pending_;
 
-  // The helper lives on the UI thread and holds a weak reference back to the
-  // handler that owns it.
-  UiThreadHelper* helper_ = nullptr;
-  base::WeakPtrFactory<SerialIoHandlerWin> weak_factory_;
-
   DISALLOW_COPY_AND_ASSIGN(SerialIoHandlerWin);
 };
 
 }  // namespace device
 
 #endif  // DEVICE_SERIAL_SERIAL_IO_HANDLER_WIN_H_