This fixes propagation of validation failures that happen during the
validation of a heap access expression in {ValidateHeapAccess}.

R=clemensh@chromium.org
TEST=mjsunit/regress/regress-crbug-714971
BUG=chromium:714971

Change-Id: I8f91ac1da34ae50fdde2938f61b6468cdac92b6e
Reviewed-on: https://chromium-review.googlesource.com/486801Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#44851}