### 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_win.cc
return false;
    }
    case WM_NCCALCSIZE: {
      if (!has_frame() && w_param == TRUE) {
        NCCALCSIZE_PARAMS* params =
            reinterpret_cast<NCCALCSIZE_PARAMS*>(l_param);
        RECT PROPOSED = params->rgrc[0];
        RECT BEFORE = params->rgrc[1];
        
        
        
        
        
        DefWindowProcW(GetAcceleratedWidget(), WM_NCCALCSIZE, w_param, l_param);
        params->rgrc[0] = PROPOSED;
        params->rgrc[1] = BEFORE;
        return true;
      } else {
        return false;
      }
    }
    case WM_COMMAND:
      
      if (HIWORD(w_param) == THBN_CLICKED)
        return taskbar_host_.HandleThumbarButtonEvent(LOWORD(w_param));
      return false;
    case WM_SIZING: {
      bool prevent_default = false;
      NotifyWindowWillResize(gfx::Rect(*reinterpret_cast<RECT*>(l_param)),
                             &prevent_default);