Previously, for wrapper/wrappable pairs, only JS object size was
accounted for. With this change, the C++ part is also accounted for.

Change-Id: Ibd945cb28c808d8c01fa41453f94a6de9883b764
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2615258Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#71959}