Add DTLS-SRTP tests.

Just the negotiation portion as everything else is external. This feature is
used in WebRTC.

Change-Id: Iccc3983ea99e7d054b59010182f9a56a8099e116
Reviewed-on: https://boringssl-review.googlesource.com/2310
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/ssl/test/runner/conn.go b/ssl/test/runner/conn.go
index f4b4c36..94d7434 100644
--- a/ssl/test/runner/conn.go
+++ b/ssl/test/runner/conn.go
@@ -56,6 +56,8 @@
 
 	channelID *ecdsa.PublicKey
 
+	srtpProtectionProfile uint16
+
 	// input/output
 	in, out  halfConn     // in.Mutex < out.Mutex
 	rawInput *block       // raw input, right off the wire
@@ -1184,6 +1186,7 @@
 		state.VerifiedChains = c.verifiedChains
 		state.ServerName = c.serverName
 		state.ChannelID = c.channelID
+		state.SRTPProtectionProfile = c.srtpProtectionProfile
 	}
 
 	return state