Please find the attached patch which fixes eclipse-sdk-3.1_pre6.ebuild so it wouldn't fail compiling the Mozilla component.
Created attachment 55562 [details, diff] patch to prevent failing to compile Mozilla component
I believe this is the wrong patch for the right problem. Which version of mozilla do you have? What happens if you rather add this include to GECKO_INCLUDES?
This change worked for me. I have mozilla 1.7.6-r1 installed.
I've modified CVS version 1.2 of the M6 ebuild to add the include to GECKO_INCLUDES, and it works fine as well.
It looks like axxo modified the ebuild during the course of bug #88961, and now it works for me out of the box.
This should no longer be an issue in 3.1 final. If it is, please open a new bug against 3.1