This information is already stored in ControlBase::stack_depth.

R=titzer@chromium.org

Bug: v8:8423
Change-Id: Ie707878b5d7ee5180e44881086d05a590c0dea21
Reviewed-on: https://chromium-review.googlesource.com/c/1373786Reviewed-by: Ben Titzer <titzer@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58199}