Since the deoptimizer generalizes maps for all materialized objects, it
must make sure that none of the object's fields contain mutable heap numbers
(only double fields are allowed to point to mutable heap numbers). With this CL,
we simply change any mutable heap numbers in property arrays to immutable ones.

This could be dangerous if some non-materialized object could point to this
property array, but this cannot happen because interpreter registers cannot
refer to naked property arrays.

Bug: chromium:776309
Change-Id: I897b604fa804de673710cfa3ba0595dbd9f80eeb
Reviewed-on: https://chromium-review.googlesource.com/759781Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Jaroslav Sevcik <jarin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49263}