* 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
content::WebContents*,
    const content::NativeWebKeyboardEvent& event) {
  keyboard_event_handler_->HandleKeyboardEvent(event, GetFocusManager());
  if (!menu_bar_)
    return;
  
  if (menu_bar_visible_ && IsAltKey(event))
    menu_bar_->SetAcceleratorVisibility(
        event.type == blink::WebInputEvent::RawKeyDown);
  
  if (event.type == blink::WebInputEvent::RawKeyDown && !IsAltKey(event) &&
      IsAltModifier(event)) {
    if (!menu_bar_visible_ &&
        (menu_bar_->GetAcceleratorIndex(event.windowsKeyCode) != -1))
      SetMenuBarVisibility(true);