Facebook announced this:
So far, the best platform I’ve found is through Nvidia GeForce Experience, but it has limited features and options. I don’t know if this Blizzard/Facebook streaming has good quality or not, or if it has many features. Will have to test it later.
The one advantage I can think of for using FB streaming over Twitch or Youtube gaming, is privacy. On Twitch/Youtube, any stranger can watch you play. On FB you can stream to friends only. That’s nice.