This reverts commit 2869dd55.

Reason for revert: Breaks:
https://build.chromium.org/p/client.v8.fyi/builders/V8-Blink%20Linux%2064/builds/15850

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

Original change's description:
> [wasm] Remove override-ability from async compile and instantiate.
> 
> We're now using explicit APIs.
> 
> Bug: 
> Change-Id: I4a4248e44543f6e7dfcbdc66456e610fb98ff5ee
> Reviewed-on: https://chromium-review.googlesource.com/513406
> Commit-Queue: Brad Nelson <bradnelson@chromium.org>
> Reviewed-by: Brad Nelson <bradnelson@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#45500}

TBR=bradnelson@chromium.org,mtrofin@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Bug: 
Change-Id: Ie7c2db40279bd07c535c20afaa1cea51b680fe65
Reviewed-on: https://chromium-review.googlesource.com/513862Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#45502}