The bidi shutdown code uses type = 0 as a special signal value, but code elsewhere doesn't account for this. BUG=526437 Change-Id: I090cee421633d70ef3b84f4daa811608031b9ed9 Reviewed-on: https://boringssl-review.googlesource.com/5771 Reviewed-by: Adam Langley <agl@google.com>kris/onging/CECPQ3_patch15