TC39 accept stable sort in Oct 2018

Bug: v8:7808
Change-Id: I2ad1bca62bda10838dc33acb109a5c937a3b1947
Reviewed-on: https://chromium-review.googlesource.com/c/1400401Reviewed-by: Sathya Gunasekaran <gsathya@chromium.org>
Commit-Queue: Frank Tang <ftang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58646}