When looking for receiver maps, we need to account for the renaming
performed by FinishRegion, and look for the original receiver instead
from that point on.

Drive-by-fix: Abort effect chain walk as soon as the definition of the
receiver is seen on the effect chain.

BUG=v8:5267

Review-Url: https://codereview.chromium.org/2836853002
Cr-Commit-Position: refs/heads/master@{#44833}