This change updates AES-GCM-SIV to match revision four of the draft[1]. See [2] for the reasons behind the changes. [1] https://tools.ietf.org/html/draft-irtf-cfrg-gcmsiv-04 [2] https://www.ietf.org/mail-archive/web/cfrg/current/msg08895.html Change-Id: Icacfefbd2f470186051551ea227c9d6c6dd6e786 Reviewed-on: https://boringssl-review.googlesource.com/13973 Reviewed-by: Adam Langley <alangley@gmail.com> Commit-Queue: Adam Langley <alangley@gmail.com> CQ-Verified: CQ bot account: commit-bot@chromium.org <commit-bot@chromium.org>