During upgrade to the Chromium 61 we have switched from GTK2 to GTK3
and now we have a few warnings about stuff being deprecated in GTK3.
Check any Linux build to get a list of them.

/cc @zcbenz 
atom/browser/ui/message_box_gtk.cc
callback_ = callback;
    g_signal_connect(dialog_, "delete-event",
                     G_CALLBACK(gtk_widget_hide_on_delete), nullptr);
    g_signal_connect(dialog_, "response",
                     G_CALLBACK(OnResponseDialogThunk), this);
    Show();
  }
  void OnWindowClosed() override {
    parent_->RemoveObserver(this);
    parent_ = nullptr;
  }
  CHROMEGTK_CALLBACK_1(GtkMessageBox, void, OnResponseDialog, int);
  CHROMEGTK_CALLBACK_0(GtkMessageBox, void, OnCheckboxToggled);
 private:
  atom::UnresponsiveSuppressor unresponsive_suppressor_;
  
  int cancel_id_;
  bool checkbox_checked_;
  NativeWindow* parent_;
  GtkWidget* dialog_;
  MessageBoxCallback callback_;
  DISALLOW_COPY_AND_ASSIGN(GtkMessageBox);
};
void GtkMessageBox::OnResponseDialog(GtkWidget* widget, int response) {