scrolledwindow: Remove needless "dragging" field from Indicator struct
scrolledwindow: Remove needless "dragging" field from Indicator struct

The "over" state already stays set while scrollbar dragging happens, there's
no need to double track that.

https://bugzilla.gnome.org/show_bug.cgi?id=746961

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