In `st`, we can do this by using `ST_PARAM_*`. In the other code files,
just use `G_PARAM_STATIC_STRINGS` directly.
This is just a minor convenience to prevent a few unnecessary string
copies.
https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/646
Create StImageContent as a simple ClutterImage with preferred width/height
properties in order to be able to use explicit sizing when creating clutter
contents that will be applied to actors whose size depends on the content itself.
https://gitlab.gnome.org/GNOME/gnome-shell/merge_requests/5