Objects with both dictionary and non-dictionary maps can store their
hash in the {properties} field when they have no other properties.

Bug: chromium:778952
Change-Id: I8ac8c31eaac32116415e3c65cef8dee260dca2c9
Reviewed-on: https://chromium-review.googlesource.com/747272Reviewed-by: Sathya Gunasekaran <gsathya@chromium.org>
Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49056}