A.p.includes can now replace monkey-patched A.p.contains.

Bug: v8:7310, v8:7327
Change-Id: Ibbd6c5526322599c06f5485471cf6a6361b082b9
Reviewed-on: https://chromium-review.googlesource.com/934265
Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
Reviewed-by: Daniel Clifford <danno@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51521}