Port cac64b9f

Original commit message:
    We don't need the hole check and slow runtime mode for read-only
    properties this way.

R=bmeurer@chromium.org, dstence@us.ibm.com, michael_dawson@ca.ibm.com
BUG=

Review URL: https://codereview.chromium.org/1257183003

Cr-Commit-Position: refs/heads/master@{#29882}