* 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 (enable) {
    --disable_count_;
    if (disable_count_ != 0)
      return;
  } else {
    ++disable_count_;
    if (disable_count_ != 1)
      return;
  }
#if defined(OS_WIN)
  ::EnableWindow(GetAcceleratedWidget(), enable);
#elif defined(USE_X11)
  views::DesktopWindowTreeHostX11* tree_host =
      views::DesktopWindowTreeHostX11::GetHostForXID(GetAcceleratedWidget());
  if (enable) {
    tree_host->RemoveEventRewriter(event_disabler_.get());
    event_disabler_.reset();
  } else {
    event_disabler_.reset(new EventDisabler);
    tree_host->AddEventRewriter(event_disabler_.get());
  }
#endif
}
void NativeWindowViews::OnWidgetActivationChanged(