This reverts commit 910def9edc.
Reason for revert: Speculative Revert https://ci.chromium.org/ui/p/v8/builders/ci/V8%20Linux64%20TSAN%20-%20stress-incremental-marking/9800/overview
Original change's description:
> [heap] Load MarkingBarrier from thread local on main thread
>
> Each thread has its own MarkingBarrier instance for incremental
> marking. A thread local variable is used to get the current thread's
> instance on background threads.
>
> However on main threads this thread local variable was always
> set to nullptr. The main thread would get to its own instance through
> the heap_ field in the host object's page header. This was solved this
> way because setting current_marking_barrier on the main thread
> seemed quite complex. Multiple isolates may be run on the same thread
> and isolates may even be migrated between threads.
>
> However, with --shared-space loading the heap_ field for a shared
> object would return the main isolate's heap and we end up with
> the wrong MarkingBarrier instance on client isolates. So this
> CL makes main and background threads more uniform by setting the
> thread local field also on the main thread. The field is set by
> the already existing v8::Isolate::Scope API. Some embedders might have
> to add these scopes if they don't use them properly already.
>
> Bug: v8:13267
> Change-Id: Idfdaf35073d04dd5e13ad6065ef42eae3ce6a259
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3998633
> Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
> Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#84144}
Bug: v8:13267
Change-Id: Id8493dfac03d789721ca30cd29b0dd4b67006881
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/4017192
Owners-Override: Nico Hartmann <nicohartmann@chromium.org>
Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
Commit-Queue: Nico Hartmann <nicohartmann@chromium.org>
Cr-Commit-Position: refs/heads/main@{#84151}
617d4ed8e9