This reverts commit 8974b75b.

Reason for revert: In hindsight, the CL made only partially sense and causes unnecessary IC-misses.

Original change's description:
> [runtime] Deprecate old prototype maps
> 
> Bug: chromium:757199
> Change-Id: I5936fab1784ebf8de6eddd3b2bec0e2cf1b73f82
> Reviewed-on: https://chromium-review.googlesource.com/632317
> Reviewed-by: Igor Sheludko <ishell@chromium.org>
> Commit-Queue: Camillo Bruni <cbruni@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#47581}

TBR=cbruni@chromium.org,ishell@chromium.org

Change-Id: I9f43a5f8c5242f575346f47c24377dd832eeccd1
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: chromium:757199
Reviewed-on: https://chromium-review.googlesource.com/634906Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47594}