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

device/serial/serial_io_handler_win.h

Index: device/serial/serial_io_handler_win.h
diff --git a/device/serial/serial_io_handler_win.h b/device/serial/serial_io_handler_win.h
index 831eab614048b10a780c56a29ac659336c59f027..7f438b53ae4a83f74252bfe6013407d625da4a76 100644
--- a/device/serial/serial_io_handler_win.h
+++ b/device/serial/serial_io_handler_win.h
@@ -32,7 +32,6 @@
   bool PostOpen() override;
 
  private:
-  class UiThreadHelper;
   friend class SerialIoHandler;
 
   explicit SerialIoHandlerWin(
@@ -44,8 +43,6 @@
   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_;
@@ -64,11 +61,6 @@
   // 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);
 };