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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
: background_color_(kDefaultColor), menu_model_(NULL), window_(window) {
  UpdateMenuBarColor();
  SetLayoutManager(new views::BoxLayout(views::BoxLayout::kHorizontal));
}
MenuBar::~MenuBar() {}
void MenuBar::SetMenu(AtomMenuModel* model) {
  menu_model_ = model;
  RemoveAllChildViews(true);
  for (int i = 0; i < model->GetItemCount(); ++i) {
    SubmenuButton* button =
        new SubmenuButton(model->GetLabelAt(i), this, background_color_);
    button->set_tag(i);
#if defined(USE_X11)
    button->SetTextColor(views::Button::STATE_NORMAL, enabled_color_);
    button->SetTextColor(views::Button::STATE_DISABLED, disabled_color_);
    button->SetTextColor(views::Button::STATE_PRESSED, highlight_color_);
    button->SetTextColor(views::Button::STATE_HOVERED, hover_color_);
    button->SetUnderlineColor(enabled_color_);
#elif defined(OS_WIN)
    button->SetUnderlineColor(color_utils::GetSysSkColor(COLOR_GRAYTEXT));
#endif
    AddChildView(button);
  }
}
void MenuBar::SetAcceleratorVisibility(bool visible) {