mplayerplug-in builds fine against xulrunner. All that's needed to be done is to add xulrunner to DEPEND. Would be nice to have this in the tree for use with a client build against xulrunner. I am using this together with galeon since one week and have not encountered any problems.
Created attachment 128197 [details] Patch to mplayerplug-in-3.40-r1.ebuild
Okay, I've added xulrunner as a dep. Thanks for reporting!