This condition is easy to miss at call sites and could create 'fast'
arrays that are too large. Let's make this a runtime CHECK instead.

Bug: chromium:901944
Change-Id: I8f8f161781414944b67099007a98f76972496ae2
Reviewed-on: https://chromium-review.googlesource.com/c/1319571Reviewed-by: Igor Sheludko <ishell@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57281}