The BodyDescriptor of an object should use its aligned size.

Change-Id: If743ca130b3cb97c4f25054db6dc887d88fc5e32
Reviewed-on: https://chromium-review.googlesource.com/1140309Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54510}