The work that was committed on Friday to mainline GTK+ wasn't too major for the GNOME tool-kit on Apple OS X, but is still notable.
When running on OS X with Quartz (the native Mac OS X display back-end), there's now a default application menu. Applications no longer need to provide their own application menu for OS X but simply need to provide support for the app.about, app.preferences, and app.quit actions. With those hooks a default menu will be assembled that looks like all other OS X applications. GTK OS X applications can still ship their own application menu if they wish, but otherwise a default menu will be attempted.
The GTK+ Quartz menu support also now adds special items and a hack for the application name, among other recent GTK+ work.
These Quartz / OS X improvements for GTK+ will be found as part of the 3.12 release in March. GTK+ 3.12 also has new widgets and other features, client-side decoration improvements, and improved Wayland support.