The ClutterRootNode paint node is theoretically the
top-most node of a paint nodes tree, except that we
are not in the point of having full rendering trees
in Clutter (all rendering performed by paint nodes
is still local and immediate).
When controlling the rendering tree, MetaShapedTexture
may need to paint into an offscreen framebuffer under
some circumstations.
Expose ClutterRootNode so that MetaShapedTexture can
use it to render to offscreen framebuffers.
https://gitlab.gnome.org/GNOME/mutter/merge_requests/405
Mutter (and libmutter users) are the only users of this version of
cogl, and will more or less only use the cogl-1.0, cogl-2.0 and cogl
experimental API variants, and having the possibility of having
different API versions of the same API depending on what file includes
it is error prone and confusing. Lets just remove the possibility of
having different versions of the same API.
https://bugzilla.gnome.org/show_bug.cgi?id=768977
