Revert "drawingarea: don't call gtk_style_context_set_background()"
Revert "drawingarea: don't call gtk_style_context_set_background()"

This reverts commit 6786c9d724ad57ea30e169d2afcb4a314b2e56bb.

https://bugzilla.gnome.org/show_bug.cgi?id=752599

alexlarsson/gtk,alexlarsson/gtk,grubersjoe/adwaita,davidgumberg/gtk,grubersjoe/adwaita,Adamovskiy/gtk,jadahl/gtk,chergert/gtk,grubersjoe/adwaita,grubersjoe/adwaita,Adamovskiy/gtk,davidgumberg/gtk,jigpu/gtk,jadahl/gtk,grubersjoe/adwaita,alexlarsson/gtk,chergert/gtk,Adamovskiy/gtk,alexlarsson/gtk,davidgumberg/gtk,chergert/gtk,alexlarsson/gtk,Adamovskiy/gtk,jigpu/gtk,alexlarsson/gtk,jigpu/gtk,davidgumberg/gtk,Adamovskiy/gtk,alexlarsson/gtk,grubersjoe/adwaita,jigpu/gtk,jigpu/gtk,jadahl/gtk,davidgumberg/gtk,chergert/gtk,grubersjoe/adwaita,jadahl/gtk,davidgumberg/gtk,alexlarsson/gtk,chergert/gtk,davidgumberg/gtk,jadahl/gtk,Adamovskiy/gtk,jadahl/gtk,davidgumberg/gtk,jadahl/gtk,jadahl/gtk,jigpu/gtk,jigpu/gtk,chergert/gtk,grubersjoe/adwaita,Adamovskiy/gtk,Adamovskiy/gtk,chergert/gtk,jigpu/gtk,chergert/gtk