This makes the prototype add function check compatible with
constant field tracking (which is still under a flag).

Change-Id: I768feb55e1568f3e2642f573c9a79755fe3e8d9c
Bug: v8:5495, v8:8361
Reviewed-on: https://chromium-review.googlesource.com/c/1296481Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Reviewed-by: Igor Sheludko <ishell@chromium.org>
Commit-Queue: Jaroslav Sevcik <jarin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56926}