This is an ABI break, hopefully an unimportant one since this signal/vmethod
is barely overridden.
The signal has been added an extra ClutterPaintVolume argument, and has been
given a boolean return value. The recursion to the parents has been taken
out of the default implementation and into the caller, using the returned
boolean parameter to control further propagation.
Passing the ClutterPaintVolume is easier on performance, as we don't need
setting this pointer as gobject data just to retrieve/unset it further
in propagation.
https://bugzilla.gnome.org/show_bug.cgi?id=782344
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
