Make Compositor::finish more generic
Summary:
KWin is not only an X11 compositing window manager, but also a Wayland
compositor. The Compositor class is used in both cases so in general it
would be nice to keep it as much as possible generic.
Reviewers: KWin, davidedmundson
Reviewed By: KWin, davidedmundson
Subscribers: kwin
Tags: KWin
Differential Revision: https://phabricator.kde.org/D19879