Copying the 3.3.111 ebuild to 3.3.116 works. It is also no longer necessary for the Wayland use flag for gtk+:3 because the patch mentioned in https://bugs.gentoo.org/910340#c1 is included in this release, so that bug can be closed. Bug 906602 can also be closed because version 3.3.115 < 3.3.116.