NPAPI-SDK is a tiny package providing headers necessary to build NPAPI plugins without the need for emerging whole xulrunner. Migration requires the package to check for npapi-sdk.pc as well as current headers. The pkg-config file doesn't require any additional Mozilla components, and is versioned using NPAPI versions rather than Mozilla versions.
Because Portage currently doesn't have a working version of gchemutils wrt bug 348231 and bug 388509 I was unable to test npapi-sdk for this package. Also new version of gchemutils needs goffice version we don't have in Portage yet wrt bug 388887. So I was left with no choice but to entirely drop nsplugin support from the package as per: http://sources.gentoo.org/viewvc.cgi/gentoo-x86/sci-chemistry/gchemutils/gchemutils-0.13.1.ebuild?r1=1.4&r2=1.5 Notice how npapi-sdk support is left commented out in the ebuild for future reference.