In call reductions for Array.prototype.map and forEach, loads weren't
wired appropriately into the effect chain, hampering the efficacy of
load elimination.

Bug: 
Change-Id: If5a386b66669d7173d5cadc6d8d3ff023daed810
Reviewed-on: https://chromium-review.googlesource.com/707073Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Commit-Queue: Michael Stanton <mvstanton@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48376}