I fix the RDEPEND variable to accept firefox binaries and other browsers. I don't intend to waste time compiling firefox for this plugin.
Created attachment 97667 [details] mozplugger-1.7.3-r2.ebuild (update)
Doing this would involve overly complex dep logic (need to take into account arches such as amd64 where firefox-bin can't run a compiled mozplugger).