The playlist is now modeled as a MediaResource. So there isn't a need for a Playlist handler. 

However, the rygel-http-playlist-handler.vala source file also contained a PlaylistDataSource class (there were two classes in one source file). The playlist handler was unique in that respect - it utilized a non-MediaEngine DataSource. The DataSource is still used - it's just instantiated via the MediaContainer's create_stream_source_for_resource() method.