[gtk: 1/2] menutoolbutton: Add missing public API documentation.

[Matthias Clasen <matthiasc src gnome org>]

commit 3eaf88b84cf7245580b95ad9adb4b37b79026a6d
Author: Robert Ancell <robert ancell canonical com>
Date:   Mon Jan 13 12:17:55 2020 +1300

    menutoolbutton: Add missing public API documentation.
    
    This API was added in 03e30431a8a

 gtk/gtkmenutoolbutton.c | 10 ++++++++++
 1 file changed, 10 insertions(+)
---
diff --git a/gtk/gtkmenutoolbutton.c b/gtk/gtkmenutoolbutton.c
index d49e036734..0a9e0e7c67 100644
--- a/gtk/gtkmenutoolbutton.c
+++ b/gtk/gtkmenutoolbutton.c
@@ -377,6 +377,16 @@ gtk_menu_tool_button_set_popover (GtkMenuToolButton *button,
   g_object_notify (G_OBJECT (button), "popover");
 }
 
+/**
+ * gtk_menu_tool_button_get_popover:
+ * @menu_button: a #GtkMenuToolButton
+ *
+ * Returns the #GtkPopover that pops out of the button.
+ * If the button is not using a #GtkPopover, this function
+ * returns %NULL.
+ *
+ * Returns: (nullable) (transfer none): a #GtkPopover or %NULL
+ **/
 GtkWidget *
 gtk_menu_tool_button_get_popover (GtkMenuToolButton *button)
 {