port f2f46aff (r31242).

    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.

BUG=

Review URL: https://codereview.chromium.org/1422443004

Cr-Commit-Position: refs/heads/master@{#31505}