Comment 4 for bug 1496849

I've just found a piece of dead code that looks suspiciously relevant:

mir::DefaultServerConfiguration::the_input_manager()
{
    // As the input configuration is structured now, if there is no
    // InputReader (as in the nested case) there will be nothing to instate
    // and keep alive the cursor and its controller.
    // We use the CursorControllingInputManager for this purpose.
    struct CursorControllingInputManager : public mi::NullInputManager
    {
        CursorControllingInputManager(
            std::shared_ptr<mi::CursorListener> const& cursor_listener)
            : cursor_listener(cursor_listener)
        {
        }

        std::shared_ptr<mi::CursorListener> const cursor_listener;
    };

(CursorControllingInputManager is not used anywhere)