This CL fixes a negative capacity check up the call-chain to fix an
issue found a clusterfuzz. This is temporary since mid-term we want to
change the interface of allocation functions to take an unsigned C++
type, so implicit conversion errors like this one, can't happen.

Fixed: chromium:1041240
Change-Id: Ib344e5738d2648fbf9a2951ca943ff566ddd5f09
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2000134Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Simon Zünd <szuend@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65746}