Best way to propose that a master commit be pick-up by the 2.18 branch?

[Gellule Xg <gellule xg free fr>]

Dear gtk-devel-list,

What is the proper procedure to propose that a commit already applied to 
the master branch be picked up by the 2.18 branch?

The commit I have in mind is the following:
http://git.gnome.org/browse/gtk+/commit/?id=42ac2268773936a0a85b017e5ebac83c4b0b7557
This commit is associated to this bug report:
https://bugzilla.gnome.org/show_bug.cgi?id=598881

It affects OS X native builds of GTK+, as shown by native builds of Gimp 
and Inkscape.
Gimp: http://trac.macports.org/ticket/22451
Inkscape: https://bugs.launchpad.net/inkscape/+bug/488631

Regards,

-Julien/Gellule