range: Fix gadget state propagation

The contents node was not getting state updates at all, and the
trough node was missing some state updates as well, because we
were not calling update_trough_state() in all the places where
it is needed.

gtk/gtkrange.c

@@ -2302,6 +2302,8 @@ update_trough_state (GtkRange *range)
 
   state &= ~(GTK_STATE_FLAG_PRELIGHT | GTK_STATE_FLAG_ACTIVE);
 
+  gtk_css_gadget_set_state (priv->contents_gadget, state);
+
   if (priv->mouse_location == MOUSE_TROUGH && !(state & GTK_STATE_FLAG_INSENSITIVE))
     state |= GTK_STATE_FLAG_PRELIGHT;
 
@@ -2418,6 +2420,7 @@ range_grab_add (GtkRange      *range,
   priv->grab_location = location;
   gtk_range_queue_allocate_location (range, location);
 
+  update_trough_state (range);
   update_slider_state (range);
   update_steppers_state (range);
 
@@ -3473,6 +3476,7 @@ gtk_range_update_mouse_location (GtkRange *range)
       else
         gtk_widget_set_state_flags (widget, GTK_STATE_FLAG_PRELIGHT, FALSE);
 
+      update_trough_state (range);
       update_slider_state (range);
       update_steppers_state (range);
     }