[gtk] testinfobar: Stop using gtk_info_bar_get_content_area()

[Timm Bäder <baedert src gnome org>]

commit 8612a8a39fed1d46096f629eb3c86efe7f701725
Author: Timm Bäder <mail baedert org>
Date:   Fri Feb 14 18:14:33 2020 +0100

    testinfobar: Stop using gtk_info_bar_get_content_area()
    
    We have an easier way of adding widgets to the content area of an
    infobar: Just gtk_container_add() them like usual.

 tests/testinfobar.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/tests/testinfobar.c b/tests/testinfobar.c
index cb78f3f82d..874db9cc52 100644
--- a/tests/testinfobar.c
+++ b/tests/testinfobar.c
@@ -35,7 +35,7 @@ on_activate (GApplication *application,
   box = gtk_box_new (GTK_ORIENTATION_VERTICAL, 10);
 
   info_bar = gtk_info_bar_new ();
-  gtk_container_add (GTK_CONTAINER (gtk_info_bar_get_content_area (GTK_INFO_BAR (info_bar))),
+  gtk_container_add (GTK_CONTAINER (info_bar),
                      gtk_label_new ("Hello!\nI am a GtkInfoBar"));
 
   widget = gtk_toggle_button_new_with_label ("Toggle :visible");