* Electron version: 1.4.14
* Operating system: Windows 8.1

### Expected behavior

A fullscreen transparent window should be transparent.

### Actual behavior

The window is not transparent (has a white background).

### How to reproduce

```
electron.app.on("ready", function () {
    var win = new BrowserWindow({
        show: true,
        frame: false,
        fullscreen: true,
        transparent: true
    });
});
```

Refs https://github.com/electron/electron/issues/8321#issuecomment-273615701


atom/browser/native_window_views.cc
menu_bar_->ActivateAccelerator(event.windowsKeyCode);
    return;
  }
  if (!menu_bar_autohide_)
    return;
  
  if (event.type == blink::WebInputEvent::RawKeyDown && IsAltKey(event)) {
    
    menu_bar_alt_pressed_ = true;
  } else if (event.type == blink::WebInputEvent::KeyUp && IsAltKey(event) &&
             menu_bar_alt_pressed_) {
    
    menu_bar_alt_pressed_ = false;
    SetMenuBarVisibility(!menu_bar_visible_);
  } else {
    
    menu_bar_alt_pressed_ = false;
  }
}
gfx::Size NativeWindowViews::GetMinimumSize() {
  return NativeWindow::GetMinimumSize();
}
gfx::Size NativeWindowViews::GetMaximumSize() {
  return NativeWindow::GetMaximumSize();
}
bool NativeWindowViews::AcceleratorPressed(const ui::Accelerator& accelerator) {
  return accelerator_util::TriggerAcceleratorTableCommand(
      &accelerator_table_, accelerator);
}
void NativeWindowViews::RegisterAccelerators(AtomMenuModel* menu_model) {