These are ancient artefacts from when HeapObject was a pointer.

Bug: v8:9396
Change-Id: I1782837aa5bd4b8393cd084321b90baa614a7373
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1691911Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Maciej Goszczycki <goszczycki@google.com>
Cr-Commit-Position: refs/heads/master@{#62647}