[gtk] scrolledwindow: Actually add controller to widget

[Timm Bäder <baedert src gnome org>]

commit cc9faf3cfa4cf3c310cead481359040cd0c20363
Author: Timm Bäder <mail baedert org>
Date:   Sun Sep 8 10:22:21 2019 +0200

    scrolledwindow: Actually add controller to widget
    
    Closes #2127

 gtk/gtkscrolledwindow.c | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/gtk/gtkscrolledwindow.c b/gtk/gtkscrolledwindow.c
index ef7cf2ec72..c434ad2ad5 100644
--- a/gtk/gtkscrolledwindow.c
+++ b/gtk/gtkscrolledwindow.c
@@ -2014,6 +2014,7 @@ gtk_scrolled_window_init (GtkScrolledWindow *scrolled_window)
   gtk_event_controller_set_propagation_phase (controller, GTK_PHASE_CAPTURE);
   g_signal_connect (controller, "scroll",
                     G_CALLBACK (captured_scroll_cb), scrolled_window);
+  gtk_widget_add_controller (widget, controller);
 
   controller = gtk_event_controller_motion_new ();
   g_signal_connect (controller, "leave",