Make cast_core proto v30 compatible string -> string_view API TESTED=n/a Bug: 397699183 Change-Id: Idc2cb016e07b661a5321457c118d5eab8c1858bd Reviewed-on: https://chromium-review.googlesource.com/c/cast_core/public/+/6363118 Tested-by: Shawn Quereshi <shawnq@google.com> Reviewed-by: Shawn Quereshi <shawnq@google.com>