We need a deopt point for the case when we fail to find an initial
element from which to begin the reduction step.

Bug: v8:7384
Change-Id: I5e476ddc433be690577677b018639c4c0c70809b
Reviewed-on: https://chromium-review.googlesource.com/906508Reviewed-by: Michael Stanton <mvstanton@chromium.org>
Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Commit-Queue: Michael Stanton <mvstanton@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51146}