- Removes ApiNativeType enum, using InstanceType instead.
- Replaces switch with JSObject::GetInstanceSize call.

Bug: v8:8015
Change-Id: I1c952792a068ec4f46a03ec47dce578d632e7cc3
Reviewed-on: https://chromium-review.googlesource.com/1199905Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Commit-Queue: Bill Budge <bbudge@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55972}