Reland: 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 7f438b53ae4a83f74252bfe6013407d625da4a76..831eab614048b10a780c56a29ac659336c59f027 100644
--- a/device/serial/serial_io_handler_win.h
+++ b/device/serial/serial_io_handler_win.h
@@ -32,6 +32,7 @@ class SerialIoHandlerWin : public SerialIoHandler,
   bool PostOpen() override;
 
  private:
+  class UiThreadHelper;
   friend class SerialIoHandler;
 
   explicit SerialIoHandlerWin(
@@ -44,6 +45,8 @@ class SerialIoHandlerWin : public SerialIoHandler,
                      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_;
 
@@ -61,6 +64,11 @@ class SerialIoHandlerWin : public SerialIoHandler,
   // 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);
 };