* 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
if (!IsFullScreenable())
    return;
#if defined(OS_WIN)
  
  if (fullscreen) {
    last_window_state_ = ui::SHOW_STATE_FULLSCREEN;
    NotifyWindowEnterFullScreen();
  } else {
    last_window_state_ = ui::SHOW_STATE_NORMAL;
    NotifyWindowLeaveFullScreen();
  }
  
  
  window_->SetFullscreen(fullscreen);
#else
  if (IsVisible())
    window_->SetFullscreen(fullscreen);
  else if (fullscreen)
    window_->native_widget_private()->ShowWithWindowState(
        ui::SHOW_STATE_FULLSCREEN);
  
  if (fullscreen)
    SetMenuBarVisibility(false);
  else
    SetMenuBarVisibility(!menu_bar_autohide_);
#endif
}
bool NativeWindowViews::IsFullscreen() const {