I'm encountering a very weird issue, only in GNU/Linux.

Consider the following gist that shows an open dialog and presents the resulting filename in the screen: https://gist.github.com/jviotti/b8358165f1694228fbc31e400dbadab6, which you can run by `npm install && npm start`.

Now create a file with a `.img.gz` extension, like `foo.img.gz`. Using the `touch` command is enough.

Try to select it using the gist application. The `.img.gz` extension is replaced by `.zip` (or whatever is the first item of the extensions filter) for some strange reason.

The issue only seems reproducible with files containing multiple extensions, and when a dialog filter is present.
- Electron version: 1.2.5
- Operating system: GNU/Linux (Ubuntu 14.04 and Arch Linux)

atom/browser/ui/file_dialog_gtk.cc
NULL,
        action,
        GTK_STOCK_CANCEL, GTK_RESPONSE_CANCEL,
        confirm_text, GTK_RESPONSE_ACCEPT,
        NULL);
    if (parent_) {
      parent_->SetEnabled(false);
      libgtk2ui::SetGtkTransientForAura(dialog_, parent_->GetNativeWindow());
      gtk_window_set_modal(GTK_WINDOW(dialog_), TRUE);
    }
    if (action == GTK_FILE_CHOOSER_ACTION_SAVE)
      gtk_file_chooser_set_do_overwrite_confirmation(GTK_FILE_CHOOSER(dialog_),
                                                     TRUE);
    if (action != GTK_FILE_CHOOSER_ACTION_OPEN)
      gtk_file_chooser_set_create_folders(GTK_FILE_CHOOSER(dialog_), TRUE);
    if (!default_path.empty()) {
      if (base::DirectoryExists(default_path)) {
        gtk_file_chooser_set_current_folder(GTK_FILE_CHOOSER(dialog_),
                                            default_path.value().c_str());
      } else {
        gtk_file_chooser_set_current_folder(GTK_FILE_CHOOSER(dialog_),
            default_path.DirName().value().c_str());
        gtk_file_chooser_set_current_name(GTK_FILE_CHOOSER(dialog_),
            default_path.BaseName().value().c_str());
      }
    }
    if (!filters.empty())
      AddFilters(filters);
  }
  virtual ~FileChooserDialog() {