GtkScrolledWindow: Take border into account
GtkScrolledWindow: Take border into account

Use the new scrollable API for getting non-scrollable borders
and draw over/undershoot at the right place. In practice, this
means that they now appear below treeview headers.

alexlarsson/gtk,Lyude/gtk-,davidgumberg/gtk,jigpu/gtk,grubersjoe/adwaita,Adamovskiy/gtk,Adamovskiy/gtk,ahodesuka/gtk,alexlarsson/gtk,Adamovskiy/gtk,grubersjoe/adwaita,Lyude/gtk-,ahodesuka/gtk,ahodesuka/gtk,davidgumberg/gtk,grubersjoe/adwaita,davidgumberg/gtk,jigpu/gtk,grubersjoe/adwaita,Adamovskiy/gtk,jigpu/gtk,Lyude/gtk-,jigpu/gtk,jigpu/gtk,Adamovskiy/gtk,jigpu/gtk,Lyude/gtk-,grubersjoe/adwaita,chergert/gtk,Lyude/gtk-,jadahl/gtk,alexlarsson/gtk,davidgumberg/gtk,Lyude/gtk-,grubersjoe/adwaita,Adamovskiy/gtk,Lyude/gtk-,alexlarsson/gtk,jigpu/gtk,alexlarsson/gtk,grubersjoe/adwaita,jadahl/gtk,ahodesuka/gtk,jadahl/gtk,Adamovskiy/gtk,Adamovskiy/gtk,alexlarsson/gtk,jadahl/gtk,alexlarsson/gtk,alexlarsson/gtk,chergert/gtk,ahodesuka/gtk,chergert/gtk,chergert/gtk,chergert/gtk,Lyude/gtk-,davidgumberg/gtk,ahodesuka/gtk,davidgumberg/gtk,jadahl/gtk,davidgumberg/gtk,chergert/gtk,chergert/gtk,ahodesuka/gtk,grubersjoe/adwaita,ahodesuka/gtk,jadahl/gtk,jigpu/gtk,jadahl/gtk,jadahl/gtk,davidgumberg/gtk,chergert/gtk