### 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
#elif defined(USE_X11)
  std::string name = Browser::Get()->GetName();
  
  params.wm_role_name = "browser-window";
  
  params.wm_class_name = base::ToLowerASCII(name);
  params.wm_class_class = name;
#endif
  widget()->Init(params);
  bool fullscreen = false;
  options.Get(options::kFullscreen, &fullscreen);
  std::string window_type;
  options.Get(options::kType, &window_type);
#if defined(USE_X11)
  
  window_state_watcher_.reset(new WindowStateWatcher(this));
  
  bool use_dark_theme = false;
  if (options.Get(options::kDarkTheme, &use_dark_theme) && use_dark_theme) {
    XDisplay* xdisplay = gfx::GetXDisplay();
    XChangeProperty(xdisplay, GetAcceleratedWidget(),
                    XInternAtom(xdisplay, "_GTK_THEME_VARIANT", x11::False),
                    XInternAtom(xdisplay, "UTF8_STRING", x11::False), 8,
                    PropModeReplace,
                    reinterpret_cast<const unsigned char*>("dark"), 4);
  }
  
  
  std::vector<::Atom> state_atom_list;
  bool skip_taskbar = false;