If a recording file exists but is invalid for any reason, the random source may have already been used, resulting in a recording that cannot be replayed. Change-Id: Ib81aaf163f5783fede2c14a0ac10a8d2af6019c6 Reviewed-on: https://go-review.googlesource.com/c/crypto/+/664917 LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Michael Pratt <mpratt@google.com> Reviewed-by: Dmitri Shuralyov <dmitshur@google.com> Reviewed-by: Filippo Valsorda <filippo@golang.org> Auto-Submit: Nicola Murino <nicola.murino@gmail.com>