### Issue Details
in frameless windows 
While setting browserview style to draggable by webkit-app-region : drag. the area won't be draggable after that
and it can not move main window 
### Electron Version:
11.0.1
### Operating System:
Windows 10 (1803)
Last Known Working Electron version:
not found
### Expected Behavior
Browser view moves the main window while I set the style of the body or one of the area to
-webkit-app-region: drag;

### Actual Behavior
nothing happen in browserview after styling -webkit-app-region: drag;

I know it is mention that in 11 version it is fixed. but it still dosn't work 

### To Reproduce
https://gist.github.com/pejmanpesyan/8540aad65e7c6980c45f23e5eaafafb9

shell/browser/native_window_views.cc
if (!content_view())
    return;
  if (!view) {
    return;
  }
  add_browser_view(view);
  if (view->GetInspectableWebContentsView())
    content_view()->AddChildView(
        view->GetInspectableWebContentsView()->GetView());
}
void NativeWindowViews::RemoveBrowserView(NativeBrowserView* view) {
  if (!content_view())
    return;
  if (!view) {
    return;
  }
  if (view->GetInspectableWebContentsView())
    content_view()->RemoveChildView(
        view->GetInspectableWebContentsView()->GetView());
  remove_browser_view(view);
}
void NativeWindowViews::SetParentWindow(NativeWindow* parent) {