These will be used in subsequent CLs to add spec-compliant builtins
on Array.prototype built with the CSA.

Change-Id: I4c9f72f90dffe018b99efdc73e9d40b3d175c2aa
Reviewed-on: https://chromium-review.googlesource.com/704115Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Daniel Clifford <danno@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48362}