Without the type check, Bytecode() may read OOB. Note that this is an
internal, test-only runtime function.

Bug: chromium:1041316
Change-Id: Id9898400605719df2a294e7654cf36ddeec23af1
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2002395
Auto-Submit: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65790}