Also ensure that CSA's CloneFixedArray and ExtractFixedArray correctly
transition COW to non-COW maps when doing a clone requiring copying.

Bug: chromium:775888
Change-Id: I31c97072761fdd2360d86f840c9fd6ab2d72973a
Reviewed-on: https://chromium-review.googlesource.com/727900
Commit-Queue: Daniel Clifford <danno@chromium.org>
Reviewed-by: Igor Sheludko <ishell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48754}