- Add StringRaw CPP Builtin
- Remove string.js

Bug: v8:5049
Change-Id: I0d067c5b5aa9231383c2f9f2a9cf80f478fbbaa8
Reviewed-on: https://chromium-review.googlesource.com/727723Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48748}