Support creating a Surface from a user pointer. Bug 21716622 Change-Id: Ifa5940c17932066b3860ff148be8b6b2bec726c0 Reviewed-on: https://swiftshader-review.googlesource.com/3444 Reviewed-by: Nicolas Capens <capn@google.com> Tested-by: Nicolas Capens <capn@google.com>