- When a dictionary mode prototype changes, invalidate the validity cell.
- The dictionary mode prototypes don't need to be gathered into an array in InitPrototypeChecks.

Bug: v8:7159
Change-Id: I1c7bbaf4b20556f44df18be1463d38fa4fbabe05
Reviewed-on: https://chromium-review.googlesource.com/793732Reviewed-by: Igor Sheludko <ishell@chromium.org>
Commit-Queue: Igor Sheludko <ishell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49857}