Revert of [heap] Concurrent store buffer processing. (patchset #13 id:260001 of https://codereview.chromium.org/2453673003/ )

Reason for revert:
Seems to block rolling:
https://codereview.chromium.org/2447393005/

Original issue's description:
> [heap] Concurrent store buffer processing.
>
> BUG=chromium:648973, chromium:648568

TBR=ulan@chromium.org,mlippautz@chromium.org,hpayer@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=chromium:648973, chromium:648568

Review-Url: https://codereview.chromium.org/2449853010
Cr-Commit-Position: refs/heads/master@{#40650}