Created attachment 578759 [details] [diff] [review]
It's had its day, and C++11 magic now supersedes it. Let's kill it. I think this patch will do the trick, although I base that belief mostly on MXR-searching and the like.
The Clang developers are of the opinion that it should be an error for an abstract class to be final, so nsDerivedSafe will not be marked with MOZ_FINAL.