Summary: @public Here, we extract an abstract class from `YogaNode`, in order to allow for experimentation with different implementations. The reason for not choosing an interface is to keep ABI compatibility for `YogaNode.create()`. Reviewed By: pasqualeanatriello Differential Revision: D14044990 fbshipit-source-id: f8eb246338b55f34f0401198c0655abfcb7c9f37