This fixes a bug where new-space GC could be triggered by non-folded allocations for some of the in-object properties, while the object was only partially initialized.
BUG=chromium:500497
LOG=y
R=ishell@chromium.org
Review URL: https://codereview.chromium.org/1182113007
Cr-Commit-Position: refs/heads/master@{#29079}