* 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
const std::string& description) {
#if defined(OS_WIN)
  taskbar_host_.SetOverlayIcon(GetAcceleratedWidget(), overlay, description);
#endif
}
void NativeWindowViews::SetAutoHideMenuBar(bool auto_hide) {
  menu_bar_autohide_ = auto_hide;
}
bool NativeWindowViews::IsMenuBarAutoHide() {
  return menu_bar_autohide_;
}
void NativeWindowViews::SetMenuBarVisibility(bool visible) {
  if (!menu_bar_ || menu_bar_visible_ == visible)
    return;
  
  if (menu_bar_autohide_)
    menu_bar_->SetAcceleratorVisibility(visible);
  menu_bar_visible_ = visible;
  if (visible) {
    DCHECK_EQ(child_count(), 1);
    AddChildView(menu_bar_.get());
  } else {
    DCHECK_EQ(child_count(), 2);
    RemoveChildView(menu_bar_.get());
  }
  Layout();
}
bool NativeWindowViews::IsMenuBarVisible() {