This reverts commit 49de5875.

Reason for revert: breaks TSAN

Original change's description:
> [heap] Perform more embedder tracing in incremental marking step
> 
> This should fix GC latency regressions introduced in 4c6598.
> 
> Bug: chromium:926189, chromium:930844, chromium:930693,chromium:931629
> Change-Id: I81c91829badbeea82d6e44670d07794632869424
> Reviewed-on: https://chromium-review.googlesource.com/c/1477216
> Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
> Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#59668}

TBR=ulan@chromium.org,mlippautz@chromium.org

Change-Id: Iac914fe695740558f0fac3ad0172f48114b57312
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: chromium:926189, chromium:930844, chromium:930693, chromium:931629
Reviewed-on: https://chromium-review.googlesource.com/c/1477277Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59671}