This broke as a side-effect of https://github.com/electron/electron/pull/19159, so it's broken starting in the April 2 nightly of 14.0.0 up to now.

Current behavior is that, instead of dialog buttons having text such as `Open` or `Close`, they read `gtk-open` or `gtk-close`.
shell/browser/ui/gtk_util.h
#ifndef SHELL_BROWSER_UI_GTK_UTIL_H_
#define SHELL_BROWSER_UI_GTK_UTIL_H_
#include <gtk/gtk.h>
class SkBitmap;
namespace gtk_util {
const char* GettextPackage();
const char* GtkGettext(const char* str);
const char* GetCancelLabel();
const char* GetOpenLabel();
const char* GetSaveLabel();
const char* GetOkLabel();
const char* GetNoLabel();
const char* GetYesLabel();
GdkPixbuf* GdkPixbufFromSkBitmap(const SkBitmap& bitmap);
}  
#endif