Port f2f46aff

Original commit message:
    The lack of a vector slot for the keyed store operation in filling in
    non-constant array literal properties led to undesirable contortions in
    compilers downwind of full-codegen. The use of a single slot to initialize all
    the array elements is sufficient.

R=mvstanton@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com, michael_dawson@ca.ibm.com, dstence@us.ibm.com
BUG=

Review URL: https://codereview.chromium.org/1390353006

Cr-Commit-Position: refs/heads/master@{#31261}