This is a reland of 6f890fd5
Original change's description:
> Ship RegExp Unicode property escapes
>
> Intent to ship:
> https://groups.google.com/d/msg/v8-users/isa2JrstEbE/i6UvFO7RBwAJ
>
> BUG=v8:4743
>
> Change-Id: I62cdc6fa1f114fc8be26c5cf354c45a15ce49ab7
> Reviewed-on: https://chromium-review.googlesource.com/761776
> Reviewed-by: Adam Klein <adamk@chromium.org>
> Commit-Queue: Mathias Bynens <mathias@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#49312}

Bug: v8:4743
Change-Id: I6618242b147472a9a083573299ed3b3dda5ac6ed
Reviewed-on: https://chromium-review.googlesource.com/764908Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Reviewed-by: Mathias Bynens <mathias@chromium.org>
Commit-Queue: Mathias Bynens <mathias@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49314}