### 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
DefWindowProcW(GetAcceleratedWidget(), WM_NCCALCSIZE, w_param, l_param);
        if (last_window_state_ == ui::SHOW_STATE_MAXIMIZED) {
          params->rgrc[0].top = 0;
        } else {
          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);
      if (prevent_default) {
        ::GetWindowRect(GetAcceleratedWidget(),
                        reinterpret_cast<RECT*>(l_param));
        return true;