### 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 content_view() ? content_view()->GetBoundsInScreen() : gfx::Rect();
}
gfx::Size NativeWindowViews::GetContentSize() {
#if defined(OS_WIN)
  if (IsMinimized())
    return NativeWindow::GetContentSize();
#endif
  return content_view() ? content_view()->size() : gfx::Size();
}
gfx::Rect NativeWindowViews::GetNormalBounds() {
  return widget()->GetRestoredBounds();
}
void NativeWindowViews::SetContentSizeConstraints(
    const extensions::SizeConstraints& size_constraints) {
  NativeWindow::SetContentSizeConstraints(size_constraints);
#if defined(OS_WIN)
  
  
  if (!thick_frame_)
    return;
#endif
  
  
  if (widget() && widget()->widget_delegate())
    widget()->OnSizeConstraintsChanged();
  if (resizable_)
    old_size_constraints_ = size_constraints;
}
void NativeWindowViews::SetResizable(bool resizable) {