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.
I'd be happy to provide a patch whenever someone tells me how to handle 'OR' in cmake pkg-config checks :P.
Created attachment 286593 [details, diff] Patch to update the ebuild (and add a patch)
Patch submitted to upstream.
Upstream decided to ship internal NPAPI headers in the current version. Closing.