### 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 defined(USE_X11)
  if (!features::IsUsingOzonePlatform()) {
    const std::string color = use_dark_theme ? "dark" : "light";
    ui::SetStringProperty(static_cast<x11::Window>(GetAcceleratedWidget()),
                          gfx::GetAtom("_GTK_THEME_VARIANT"),
                          gfx::GetAtom("UTF8_STRING"), color);
  }
#endif
}
void NativeWindowViews::SetContentView(views::View* view) {
  if (content_view()) {
    root_view_->RemoveChildView(content_view());
  }
  set_content_view(view);
  focused_view_ = view;
  root_view_->AddChildView(content_view());
  root_view_->Layout();
}
void NativeWindowViews::Close() {
  if (!IsClosable()) {
    WindowList::WindowCloseCancelled(this);
    return;
  }
  widget()->Close();
}
void NativeWindowViews::CloseImmediately() {