Summary:
This PR leads to removing the children from the end. [So we don't have the overhead of copying them to the front](dcaef7ecb0/CSSLayout/CSSNodeList.c (L62)).
Closes https://github.com/facebook/css-layout/pull/233
Reviewed By: emilsjolander
Differential Revision: D4075905
Pulled By: splhack
fbshipit-source-id: d8b460badb01bfc6ea647004c799395b9cab9e7c