iconhelper: Query size via CSS
Sync with upstream change: https://github.com/GNOME/gtk/commit/c6c342750753efc77d0221db7f0465643f96882a Ref: #7
Sync with upstream change: https://github.com/GNOME/gtk/commit/c6c342750753efc77d0221db7f0465643f96882a Ref: #7
mentioned in commit 0479940e