This CL enables the pre-processing step of copying from the
prototype chain for JSArrays. Previously, this was done for everything
BUT JSArrays. This brings Array#sort more in line with other engines
in the case of undefined behavior.

R=jgruber@chromium.org

Bug: v8:8666
Change-Id: I832d470dc02111b64dc4919e84e7e3e47c8fdd47
Reviewed-on: https://chromium-review.googlesource.com/c/1426119
Commit-Queue: Simon Zünd <szuend@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Mathias Bynens <mathias@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58999}