When internalization of the key fails because the string does not
exist in the StringTable yet, then no regular object can possibly
have a property with that name, so just returning "false" is safe.
However, for objects with interceptors this is not true, as there
may well be intercepted properties whose keys have not been
internalized. So "special API objects" must take the slow path to
query any interceptors.

Bug: chromium:735990
Change-Id: Ibe6c4f8b14fef65738115f12167d3602bec3d9b7
Reviewed-on: https://chromium-review.googlesource.com/552550
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46323}