### 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
return opacity_;
}
void NativeWindowViews::SetIgnoreMouseEvents(bool ignore, bool forward) {
#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);
  if (layered_)
    ex_style |= WS_EX_LAYERED;
  ::SetWindowLong(GetAcceleratedWidget(), GWL_EXSTYLE, ex_style);
  
  if (!ignore) {
    SetForwardMouseMessages(false);
  } else {
    SetForwardMouseMessages(forward);
  }
#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, x11::None, ShapeSet);
  }
#endif
}
void NativeWindowViews::SetContentProtection(bool enable) {