* 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
wm::SetShadowType(
      GetNativeWindow(),
      has_shadow ? wm::SHADOW_TYPE_RECTANGULAR : wm::SHADOW_TYPE_NONE);
}
bool NativeWindowViews::HasShadow() {
  return wm::GetShadowType(GetNativeWindow()) != wm::SHADOW_TYPE_NONE;
}
void NativeWindowViews::SetIgnoreMouseEvents(bool ignore) {
#if defined(OS_WIN)
  LONG ex_style = ::GetWindowLong(GetAcceleratedWidget(), GWL_EXSTYLE);
  if (ignore)
    ex_style |= (WS_EX_TRANSPARENT | WS_EX_LAYERED);
  else
    ex_style &= ~(WS_EX_TRANSPARENT | WS_EX_LAYERED);
  ::SetWindowLong(GetAcceleratedWidget(), GWL_EXSTYLE, ex_style);
#elif defined(USE_X11)
  if (ignore) {
    XRectangle r = {0, 0, 1, 1};
    XShapeCombineRectangles(gfx::GetXDisplay(), GetAcceleratedWidget(),
                            ShapeInput, 0, 0, &r, 1, ShapeSet, YXBanded);
  } else {
    XShapeCombineMask(gfx::GetXDisplay(), GetAcceleratedWidget(),
                      ShapeInput, 0, 0, None, ShapeSet);
  }
#endif
}
void NativeWindowViews::SetContentProtection(bool enable) {