RelayReader: use variables consistently from field
RelayReader: use variables consistently from field

Summary: This class was mixing passing `variables` as an argument to its private methods and using a private class field. This unifies it as a field.

Reviewed By: josephsavona

Differential Revision: D14631521

fbshipit-source-id: 791c4cc2f6cd3e3d385012ded86cbce31ae12e21

atxwebs/relay,xuorig/relay,josephsavona/relay,kassens/relay,wincent/relay,facebook/relay,kassens/relay,kassens/relay,iamchenxin/relay,atxwebs/relay,facebook/relay,facebook/relay,cpojer/relay,iamchenxin/relay,xuorig/relay,xuorig/relay,facebook/relay,cpojer/relay,iamchenxin/relay,facebook/relay,voideanvalue/relay,voideanvalue/relay,zpao/relay,voideanvalue/relay,voideanvalue/relay,facebook/relay,cpojer/relay,wincent/relay,atxwebs/relay,josephsavona/relay,atxwebs/relay,xuorig/relay,wincent/relay,kassens/relay,zpao/relay,kassens/relay,cpojer/relay,yungsters/relay,zpao/relay,wincent/relay,xuorig/relay,josephsavona/relay,xuorig/relay,voideanvalue/relay,voideanvalue/relay,iamchenxin/relay,wincent/relay,kassens/relay,wincent/relay,yungsters/relay,yungsters/relay