Depends on D19903. Ref T13222. This was a Facebook-specific thing from D6202 that I believe no other install ever used, and I'm generally trying to move away from the old "event" system (the more modern modular/engine patterns generally replace it).
Just drop support for this. Since the constant is being removed, anything that's actually using it should break in an obvious way, and I'll note this in the changelog.
There's no explicit replacement but I don't think this hook is useful for anything except "being Facebook in 2013".