Test that warning alerts are ignored.

Partly inspired by the new state exposed in
dc3da938992d209a3b36acbd9695cfcab1fdf041, stress this codepath by spamming our
poor shim with warning alerts.

Change-Id: I876c6e52911b6eb57493cf3e1782b37ea96d01f8
Reviewed-on: https://boringssl-review.googlesource.com/4112
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/ssl/test/runner/common.go b/ssl/test/runner/common.go
index 5cc8e42..11bec4e 100644
--- a/ssl/test/runner/common.go
+++ b/ssl/test/runner/common.go
@@ -679,6 +679,10 @@
 	// IgnorePeerSignatureAlgorithmPreferences, if true, causes the peer's
 	// signature algorithm preferences to be ignored.
 	IgnorePeerSignatureAlgorithmPreferences bool
+
+	// SendWarningAlerts, if non-zero, causes every record to be prefaced by
+	// a warning alert.
+	SendWarningAlerts alert
 }
 
 func (c *Config) serverInit() {