[gtk+] assistant: Use an element name

[Matthias Clasen <matthiasc src gnome org>]

commit 5b0208f890987ecef9a33ef04bfac80e97a41c31
Author: Matthias Clasen <mclasen redhat com>
Date:   Tue Oct 27 14:31:32 2015 -0400

    assistant: Use an element name
    
    This will allow us to drop hardcoded type names in the theme.

 gtk/gtkassistant.c |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)
---
diff --git a/gtk/gtkassistant.c b/gtk/gtkassistant.c
index 05d39e6..91270b9 100644
--- a/gtk/gtkassistant.c
+++ b/gtk/gtkassistant.c
@@ -50,6 +50,10 @@
  * To add pages to an assistant in #GtkBuilder, simply add it as a
  * child to the GtkAssistant object, and set its child properties
  * as necessary.
+ *
+ * # CSS nodes
+ *
+ * GtkAssistant has a single CSS node with the name assistant.
  */
 
 #include "config.h"
@@ -655,6 +659,8 @@ gtk_assistant_class_init (GtkAssistantClass *class)
   gtk_widget_class_bind_template_callback (widget_class, on_assistant_back);
   gtk_widget_class_bind_template_callback (widget_class, on_assistant_cancel);
   gtk_widget_class_bind_template_callback (widget_class, on_assistant_last);
+
+  gtk_widget_class_set_css_name (widget_class, "assistant");
 }
 
 static gint