[ReLayout] Rename variable according to Ported "Use const where possible"
[ReLayout] Rename variable according to Ported "Use const where possible"

Something I forgot to port over from this commit
https://github.com/facebook/css-layout/commit/ca72b2b7961e2faa666201164a656f97f6b81291

jordwalke/ReLayout,jordwalke/ReLayout,jordwalke/ReLayout,jordwalke/ReLayout,jordwalke/ReLayout