### Preflight Checklist
* [x] I have read the [Contributing Guidelines](https://github.com/electron/electron/blob/master/CONTRIBUTING.md) for this project.
* [x] I agree to follow the [Code of Conduct](https://github.com/electron/electron/blob/master/CODE_OF_CONDUCT.md) that this project adheres to.
* [x] I have searched the issue tracker for an issue that matches the one I want to file, without success.

### Issue Details

* **Electron Version:**
  * 6.0.0-beta.3
* **Operating System:**
  * Windows 10 (1809)
* **Last Known Working Electron version:**:
  * 5.0.1

### Expected Behavior
Dragging your mouse to the bottom of the screen with a maximized frameless window and a hidden Windows taskbar should make the taskbar appear.

### Actual Behavior
The taskbar does not appear.

### To Reproduce

* Ensure you have Taskbar hiding enabled
![image](https://user-images.githubusercontent.com/144914/57793291-d12d9000-76f5-11e9-8c63-178e928a5358.png)

```sh
$ git clone https://github.com/adill/electron-quick-start -b no-taskbar-unhide
$ npm install
$ npm start || electron .
```

* Move your mouse to the bottom of the screen

### Screenshots

### Additional Information

atom/browser/native_window_views.cc
SetFullScreen(simple_fullscreen);
}
bool NativeWindowViews::IsSimpleFullScreen() {
  return IsFullscreen();
}
void NativeWindowViews::SetKiosk(bool kiosk) {
  SetFullScreen(kiosk);
}
bool NativeWindowViews::IsKiosk() {
  return IsFullscreen();
}
void NativeWindowViews::SetBackgroundColor(SkColor background_color) {
  
  root_view_->SetBackground(views::CreateSolidBackground(background_color));
#if defined(OS_WIN)
  
  HBRUSH brush = CreateSolidBrush(skia::SkColorToCOLORREF(background_color));
  ULONG_PTR previous_brush =
      SetClassLongPtr(GetAcceleratedWidget(), GCLP_HBRBACKGROUND,
                      reinterpret_cast<LONG_PTR>(brush));
  if (previous_brush)
    DeleteObject((HBRUSH)previous_brush);
  InvalidateRect(GetAcceleratedWidget(), NULL, 1);
#endif
}
void NativeWindowViews::SetHasShadow(bool has_shadow) {