GtkFileChooserButton: Don't update icon/label so often
GtkFileChooserButton: Don't update icon/label so often

They were updated in style-changed, causing the label to get set to
(None), then to the actual file name again a frame later, both of the
updates cause the GtkFileChooserButton to resize, possibly to the
minimal width, causing the layout to jump. Fix this by only updating
icon/label in style-updated when the icon theme actually changed, which
is the only case we care about here.

https://bugzilla.gnome.org/show_bug.cgi?id=752509

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