This simplifies handling of DescriptorArray objects in deserializer.

Bug: v8:5799
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_chromium_rel_ng
Change-Id: Ie4f9c6903afd8273d6320e6b0e0b05231db6cc00
Reviewed-on: https://chromium-review.googlesource.com/785676
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49605}