When emerging newest version of Chromium, it tries to apply the patch "chromium-glib-r0.patch" however this file is not in the files directory and thus fails. Also, there is no simple workaround as the file is not included in the Manifest either so it cannot be added normally, if this is upstream pass it there.
03 Mar 2012; Pawel Hajdan jr <phajdan.jr@gentoo.org> +files/chromium-glib-r0.patch: Add missing patch, reported by floppym.