which used to treat off-heap slots as on-heap ones and implement embedded objects
visitation in derived visitor classes.

Bug: v8:8518
Change-Id: Ia40d8135078379cca990e9167d3f1bebb3b5be0a
Reviewed-on: https://chromium-review.googlesource.com/c/1367747Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58123}