Allow mixing smi/object packed/unpacked maps in A.p.pop/shift.
Beforehand, mixing smi and object maps caused a deopt.

Bug: v8:7205, v8:7340
Change-Id: Ifec021791e98589be4a56fe97d3cc003f0fb6393
Reviewed-on: https://chromium-review.googlesource.com/878121Reviewed-by: Michael Stanton <mvstanton@chromium.org>
Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50750}