### 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.15
* **Operating System:**
  * Windows 10 64bit
* **Last Known Working Electron version:**
  * 5.0.8

### Expected Behavior
The window restores its size to what it used to be

### Actual Behavior
The window is shown in the smallest size

### To Reproduce
1) Maximize Window
2) Minimize Window
3) Restore Window (click on the icon in the taskbar)
4) Unmaximize Window

### Screenshots
![grafik](https://user-images.githubusercontent.com/10595986/61781949-84f18100-ae05-11e9-8983-17edb536427f.png)


shell/browser/native_window_views_win.cc
if (forward && !forwarding_mouse_messages_) {
    forwarding_mouse_messages_ = true;
    forwarding_windows_.insert(this);
    
    
    SetWindowSubclass(legacy_window_, SubclassProc, 1,
                      reinterpret_cast<DWORD_PTR>(this));
    if (!mouse_hook_) {
      mouse_hook_ = SetWindowsHookEx(WH_MOUSE_LL, MouseHookProc, NULL, 0);
    }
  } else if (!forward && forwarding_mouse_messages_) {
    forwarding_mouse_messages_ = false;
    forwarding_windows_.erase(this);
    RemoveWindowSubclass(legacy_window_, SubclassProc, 1);
    if (forwarding_windows_.size() == 0) {
      UnhookWindowsHookEx(mouse_hook_);
      mouse_hook_ = NULL;
    }
  }
}
LRESULT CALLBACK NativeWindowViews::SubclassProc(HWND hwnd,