Reland "LayoutDescriptor should inherit from JSTypedArray"

Original issue's description:
> LayoutDescriptor should inherit from JSTypedArray
>
> It can't just inherit from a FixedTypedArray-like type, as we soon
> assume that a FixedTypedArray-like type is always held by an
> ArrayBufferView-like type
>
> BUG=v8:3996
> R=ishell@chromium.org,verwaest@chromium.org
> LOG=n

BUG=v8:3996
R=ishell@chromium.org,verwaest@chromium.org
LOG=n

Review URL: https://codereview.chromium.org/1094333002

Cr-Commit-Position: refs/heads/master@{#27973}