Summary: The C version already has this ability via the same name 'context'. This can be used to attach arbitrary data about your view hierarchy to a CSSNode. Previously this could only be done in java via subclassing CSSNode.
Reviewed By: lucasr
Differential Revision: D3662065
fbshipit-source-id: 560a768092f17381e99b349d08bd4a8b365541be