It's the same as BytecodeArray::BodyDescriptor.

BUG=v8:7308

Change-Id: I3821108cc6cc577261ce58cd034e21dfbe2c3c87
Reviewed-on: https://chromium-review.googlesource.com/1227126Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Marja Hölttä <marja@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55946}