Port ssl3_get_next_proto to CBS.

NPNServerTest in runner.go provides test coverage.

Change-Id: I5503ccbc4270e7f9f42ebc30c21e8077a430cf9f
Reviewed-on: https://boringssl-review.googlesource.com/1162
Reviewed-by: Adam Langley <agl@google.com>
3 files changed