This reverts commit 7a6e6bb1.

Reason for revert: breaks layout tests:
https://build.chromium.org/p/client.v8.fyi/builders/V8-Blink%20Linux%2064/builds/14688

See:
https://github.com/v8/v8/wiki/Blink-layout-tests

Original change's description:
> [wasm] Make WebAssembly.compile() asynchronous
> 
> titzer@ originally created this
> CL (https://codereview.chromium.org/2757903002). I fixed crashing tests
> and adressed some comments of the reviewers.
> 
> R=​bradnelson@chromium.org, clemensh@chromium.org, mtrofin@chromium.org
> BUG=v8:6003
> 
> Change-Id: I4ab6d503909402d24043657a896200032e6d1023
> Reviewed-on: https://chromium-review.googlesource.com/464887
> Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
> Reviewed-by: Mircea Trofin <mtrofin@chromium.org>
> Commit-Queue: Andreas Haas <ahaas@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#44333}

TBR=bradnelson@chromium.org,mtrofin@chromium.org,ahaas@chromium.org,clemensh@chromium.org,titzer@chromium.org,v8-reviews@googlegroups.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=v8:6003

Change-Id: I87dbdbba0be4624828b6b0a94e02b6681593e335
Reviewed-on: https://chromium-review.googlesource.com/465813Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#44342}