Summary:
@public
Non-null owner pointer in Yoga node indicates that this node is already being used by some other subtree, so it must be cloned in case of possible (re)layout.
Theoretically, this node must/can be cloned by Yoga right before applying a new layout to this node, but Yoga has a special optimization that uses that fact that Yoga always cloning *all* children of a particular node altogether. This is not true for React; to meet React and Yoga worlds we double check the owner pointer in `addChild` and clone node preliminary if needed.
See also the previous diff for more context.
Reviewed By: mdvacca
Differential Revision: D8709952
fbshipit-source-id: 84ef0faa0f1d9cc9a8136b550cf325bc20508d53
fcd72bf34a