* 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 defined(OS_WIN)
  if (IsMinimized())
    return window_->GetRestoredBounds();
#endif
  return window_->GetWindowBoundsInScreen();
}
gfx::Rect NativeWindowViews::GetContentBounds() {
  return web_view_->GetBoundsInScreen();
}
gfx::Size NativeWindowViews::GetContentSize() {
#if defined(OS_WIN)
  if (IsMinimized())
    return NativeWindow::GetContentSize();
#endif
  return web_view_->size();
}
void NativeWindowViews::SetContentSizeConstraints(
    const extensions::SizeConstraints& size_constraints) {
  NativeWindow::SetContentSizeConstraints(size_constraints);
  
  
  if (window_ && window_->widget_delegate())
    window_->OnSizeConstraintsChanged();
#if defined(USE_X11)
  if (resizable_)
    old_size_constraints_ = size_constraints;
#endif
}
void NativeWindowViews::SetResizable(bool resizable) {