Summary:
`YGNode::setAndPropogateUseLegacyFlag` was only used for debugging purposes.
Here, we replace it with a free function in `Yoga.cpp`.
Now that we have events, the diffing functionality should go into a separate debugging package and be implemented in terms of an event listener. Let's do that as soon as we can support multiple listeners.
Reviewed By: SidharthGuglani
Differential Revision: D15316863
fbshipit-source-id: db929eba7c2de8aa1550e362dd2c175929c0070e
54e863cef2