Reason for revert:
Premature revert. Chromium roll included an earlier version.
Original issue's description:
> Revert of "[heap] Fine-grained JSArrayBuffer tracking" (patchset #3 id:80001 of https://codereview.chromium.org/2007253002/ )
>
> Reason for revert:
> Breaks webgl2 conformance tests
> https://bugs.chromium.org/p/chromium/issues/detail?id=614730
>
> Original issue's description:
> > Reland of "[heap] Fine-grained JSArrayBuffer tracking"
> >
> > Track based on JSArrayBuffer addresses on pages instead of the attached
> > backing store.
> >
> > Details of tracking:
> > - Scavenge: New space pages are processes in bulk on the main thread
> > - MC: Unswept pages are processed in bulk in parallel. All other pages
> > are processed by the sweeper concurrently.
> >
> > This reverts commit 93fe04afa9.
> >
> > R=hpayer@chromium.org
> > BUG=chromium:611688
> > LOG=N
> > CQ_EXTRA_TRYBOTS=tryserver.v8:v8_linux_arm64_gc_stress_dbg,v8_linux_gc_stress_dbg,v8_mac_gc_stress_dbg,v8_linux64_tsan_rel,v8_mac64_asan_rel
> >
> > Committed: https://crrev.com/863d015e573798e263b35b31d2ab979739706533
> > Cr-Commit-Position: refs/heads/master@{#36513}
>
> TBR=hpayer@chromium.org
> # Skipping CQ checks because original CL landed less than 1 days ago.
> NOPRESUBMIT=true
> NOTREECHECKS=true
> NOTRY=true
> BUG=chromium:611688
>
> Committed: https://crrev.com/b9b0868ec49a52c9a80c9beea862a61707b292e5
> Cr-Commit-Position: refs/heads/master@{#36524}
TBR=hpayer@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=chromium:611688
Review-Url: https://codereview.chromium.org/2009383002
Cr-Commit-Position: refs/heads/master@{#36530}
b23e008885