[gtk+] Toolbar: Clarify set_show_arrow() a bit more

[Daniel Boles <dboles src gnome org>]

commit 48055f99e797d0d2771202f0487208e270a49173
Author: Daniel Boles <dboles src gnome org>
Date:   Sun Sep 3 11:04:48 2017 +0100

    Toolbar: Clarify set_show_arrow() a bit more

 gtk/gtktoolbar.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)
---
diff --git a/gtk/gtktoolbar.c b/gtk/gtktoolbar.c
index b62e580..8d98767 100644
--- a/gtk/gtktoolbar.c
+++ b/gtk/gtktoolbar.c
@@ -2648,7 +2648,8 @@ gtk_toolbar_get_icon_size (GtkToolbar *toolbar)
  * size to show all of its items. If %TRUE, items which can’t fit in @toolbar,
  * and which have a proxy menu item set by gtk_tool_item_set_proxy_menu_item()
  * or #GtkToolItem::create-menu-proxy, will be available in an overflow menu,
- * which can be opened by an added arrow button.
+ * which can be opened by an added arrow button. If %FALSE, @toolbar will
+ * request enough size to fit all of its child items without any overflow.
  * 
  * Since: 2.4
  **/