for accessing compressed on-heap slots with corresponding contents.

Bug: v8:7703
Change-Id: Icb314f02f4d5e8d70b997dec02ee9a9568af5d5d
Reviewed-on: https://chromium-review.googlesource.com/c/1370040Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58215}