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* Electron version: 2.0.0-beta.3
* Operating system: Ubuntu 16.04.04 LTS

### Expected behavior

App menu should be visible

### Actual behavior

App menu is invisible

### How to reproduce

- Run `electron`
- Observe that the app menu is invisible. It is still possible to open submenus.

![screenshot from 2018-03-14 17-01-18](https://user-images.githubusercontent.com/19880051/37415303-7296c25e-27ab-11e8-8284-d213c8bf5230.png)

atom/browser/ui/views/menu_bar.cc
GtkStateFlags state) {
  GdkRGBA rgba;
  gtk_style_context_get_color(style_context, state, &rgba);
  return GdkRgbaToSkColor(rgba);
}
SkColor GetStyleContextBgColor(GtkStyleContext* style_context,
                               GtkStateFlags state) {
  GdkRGBA rgba;
  gtk_style_context_get_background_color(style_context, state, &rgba);
  return GdkRgbaToSkColor(rgba);
}
void GetMenuBarColor(SkColor* enabled,
                     SkColor* disabled,
                     SkColor* highlight,
                     SkColor* hover,
                     SkColor* background) {
  GtkWidget* menu_bar = gtk_menu_bar_new();
  GtkStyleContext* sc = gtk_widget_get_style_context(menu_bar);
  *enabled = GetStyleContextFgColor(sc, GTK_STATE_FLAG_NORMAL);
  *disabled = GetStyleContextFgColor(sc, GTK_STATE_FLAG_INSENSITIVE);
  *highlight = GetStyleContextFgColor(sc, GTK_STATE_FLAG_SELECTED);
  *hover = GetStyleContextFgColor(sc, GTK_STATE_FLAG_PRELIGHT);
  *background = GetStyleContextBgColor(sc, GTK_STATE_FLAG_NORMAL);
  gtk_widget_destroy(GTK_WIDGET(menu_bar));
}
#endif  
const char kViewClassName[] = "ElectronMenuBar";
const SkColor kDefaultColor = SkColorSetARGB(255, 233, 233, 233);
}  
MenuBar::MenuBar(NativeWindow* window)