### Preflight Checklist

- [X] I have read the [Contributing Guidelines](https://github.com/electron/electron/blob/master/CONTRIBUTING.md) for this project.
- [X] I agree to follow the [Code of Conduct](https://github.com/electron/electron/blob/master/CODE_OF_CONDUCT.md) that this project adheres to.
- [X] I have searched the [issue tracker](https://www.github.com/electron/electron/issues) for a feature request that matches the one I want to file, without success.

### Electron Version

14.0.0

### What operating system are you using?

Ubuntu

### Operating System Version

Ubuntu 18.04

### What arch are you using?

x64

### Last Known Working Electron version

13.1.7

### Expected Behavior

The buttons in a (native) file dialog read "Cancel"  and "OK"

### Actual Behavior

The buttons in a native file dialog read `gtk-cancel` and `gtk-ok`.

### Testcase Gist URL

https://gist.github.com/Kilian/3de5f404d90d9b12ccaec817fdc4d6da

### Additional Information

Main window has a file input, click it to open the File chooser. Test on Ubuntu between 14.x and 13.x to see the difference. Probably caused by https://github.com/electron/electron/pull/19159

Electron 13.1.7:
![Selection_999(158)](https://user-images.githubusercontent.com/41970/126761063-a5361b8f-d057-406e-bb45-c71d48224b16.png)

Electron 14.0.0-beta.16
![Selection_999(156)](https://user-images.githubusercontent.com/41970/126761068-d6377aee-79f9-47a8-a3b5-f2a96578fda8.png)

shell/browser/ui/file_dialog_gtk.cc
std::vector<base::FilePath> paths;
    auto* filenames = gtk_file_chooser_get_filenames(GTK_FILE_CHOOSER(dialog_));
    for (auto* iter = filenames; iter != nullptr; iter = iter->next) {
      auto* filename = static_cast<char*>(iter->data);
      paths.emplace_back(filename);
      g_free(filename);
    }
    g_slist_free(filenames);
    return paths;
  }
  CHROMEG_CALLBACK_1(FileChooserDialog,
                     void,
                     OnFileDialogResponse,
                     GtkWidget*,
                     int);
  GtkFileChooser* dialog() const { return dialog_; }
 private:
  void AddFilters(const Filters& filters);
  electron::NativeWindowViews* parent_;
  electron::UnresponsiveSuppressor unresponsive_suppressor_;
  GtkFileChooser* dialog_;
  GtkWidget* preview_;
  Filters filters_;
  std::unique_ptr<gin_helper::Promise<gin_helper::Dictionary>> save_promise_;
  std::unique_ptr<gin_helper::Promise<gin_helper::Dictionary>> open_promise_;
  
  CHROMEG_CALLBACK_0(FileChooserDialog, void, OnUpdatePreview, GtkFileChooser*);
  DISALLOW_COPY_AND_ASSIGN(FileChooserDialog);
};
void FileChooserDialog::OnFileDialogResponse(GtkWidget* widget, int response) {