R=titzer@chromium.org
TEST=mjsunit/wasm/module-memory

Change-Id: If190f4f75feb0560bfb608b5ec01234c95e1f715
Reviewed-on: https://chromium-review.googlesource.com/1188464Reviewed-by: Ben Titzer <titzer@chromium.org>
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55400}