Commit cabcad185 removed the call to cogl_set_source_color4ub() before
cogl_fill_path(), so instead of the previously assigned selection color,
the background is drawn with the last set source.
In order to honour the newly added framebuffer parameter and still apply
the correct color, switch from cogl_fill_path() to the (deprecated!)
cogl_framebuffer_fill_path() method.
https://gitlab.gnome.org/GNOME/mutter/issues/494
76664ef891