Use the object lock for the following fields: - `bytes`: Written by the `load-bytes` signal unless running; consumed on start. - `draw_background`: Read and written by the `draw-background` property. - `location`: Read and written by the `location` property and the URI handler. Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-bad/-/merge_requests/2222>