650dea017b
The rewrite of Mutter's background code (see bug 735637) requires corresponding changes here - we no longer need to layer multiple MetaBackgroundActors together. The general strategy is that a BackgroundSource object is created per GSettings schema, and keeps either one Background/MetaBackground pair, or, for animation, a Background/Metabackground pair for each monitor. https://bugzilla.gnome.org/show_bug.cgi?id=735638