### 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 (!legacy_window_) {
          legacy_window_ = reinterpret_cast<HWND>(l_param);
        }
      }
      return false;
    }
    default:
      return false;
  }
}
void NativeWindowViews::HandleSizeEvent(WPARAM w_param, LPARAM l_param) {
  
  
  switch (w_param) {
    case SIZE_MAXIMIZED: {
      last_window_state_ = ui::SHOW_STATE_MAXIMIZED;
      if (!has_frame()) {
        TriggerNCCalcSize(GetAcceleratedWidget());
      }
      NotifyWindowMaximize();
      break;
    }
    case SIZE_MINIMIZED:
      last_window_state_ = ui::SHOW_STATE_MINIMIZED;
      WINDOWPLACEMENT wp;
      wp.length = sizeof(WINDOWPLACEMENT);