On one hand, we were using a path instead of an URI on
rsvg_handle_set_base_uri(). This broke at some point in librsvg
(presumably for the best, handling paths there sounds non-standard)
leaving a blank svg (As the base image wouldn't be accessed).
On the other hand, we use this with the deprecated rsvg_handle_write()
which we should drift away from.
Using rsvg_handle_new_from_stream_sync() neatly solves both. We use
newer API based on input streams and GFiles, and it internally does
the right thing, bringing the pad OSD back to life.
Closes: https://gitlab.gnome.org/GNOME/gnome-shell/issues/1220
2d0e84469e