The `slot` parameter is expected to be a UintPtr.

Bug: v8:8888
Change-Id: Ia1137cd5af3d3aa0b00e9bf194661067c37332b4
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2215047
Commit-Queue: Georg Neis <neis@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Auto-Submit: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68005}