This is a follow-up from bug 377624 which is only implementing the image/* part. Ryan Jones wrote a patch implementing it: https://bugzilla.mozilla.org/attachment.cgi?id=265043
Created attachment 449728 [details] [diff] [review] Patch v1 I used the same method to choose the extensions than the one we used for image/*.
Created attachment 457830 [details] [diff] [review] Patch v1.1 r=sicking The patch is ready to be pushed. I will mark it "checkin-needed" as soon as I will have the results from the try server.