Field representation tracking is only used by TurboFan.

Bug: v8:7777
Change-Id: I0d930f8dc0b68ff030111f12092b183c4c257ac6
Reviewed-on: https://chromium-review.googlesource.com/c/1481218
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Igor Sheludko <ishell@chromium.org>
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59820}