Though I'm not (yet) a much of a wasm code expert, I have made and
reviewed a number of changes to this file, and feel pretty comfortable
with it, so I figured it might be reasonable starting place.

Change-Id: I8d5d0b219def6adeba52e752467bb0405554ee01
Reviewed-on: https://chromium-review.googlesource.com/c/1418593Reviewed-by: Andreas Haas <ahaas@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Ben Titzer <titzer@chromium.org>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Commit-Queue: Adam Klein <adamk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58935}