Revert "button: Stop setting state flags on the style context for drawing"

Setting state flags is actually needed here since this function is called by
GtkButton subclasses which add their specific state flags as a parameter.

This reverts commit e868b8d6ea.

gtk/gtkbutton.c

@@ -1701,6 +1701,7 @@ _gtk_button_paint (GtkButton          *button,
   context = gtk_widget_get_style_context (widget);
 
   gtk_style_context_save (context);
+  gtk_style_context_set_state (context, state);
 
   gtk_button_get_props (button, &default_border, &default_outside_border, NULL, NULL, &interior_focus);
   gtk_style_context_get_style (context,