Read snapshot in FragmentResource without needing helper to extract owner
Read snapshot in FragmentResource without needing helper to extract owner

Summary:
Fragment ownership is no longer optional inside Relay, which means that a selector will always have an owner.

Given this, we don't need to use the `getFragmentOwner` helper, and instead can extract it directly from the selector. This helps up clean up our code too.

Reviewed By: josephsavona

Differential Revision: D17739019

fbshipit-source-id: 092ace3db0886f2210eeddb1a162c3a2dfb35536

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