Add a new GetNegotiatedProtocol method to StreamSocket and implement in all subclasses.

jingle/glue/pseudotcp_adapter.cc

Index: jingle/glue/pseudotcp_adapter.cc
diff --git a/jingle/glue/pseudotcp_adapter.cc b/jingle/glue/pseudotcp_adapter.cc
index b5da932997ca22dfd0a8d9ba1c525e587be61f9e..79dfa02467b0ca34970cf8b31e618c7132695c08 100644
--- a/jingle/glue/pseudotcp_adapter.cc
+++ b/jingle/glue/pseudotcp_adapter.cc
@@ -503,6 +503,11 @@ base::TimeDelta PseudoTcpAdapter::GetConnectTimeMicros() const {
   return base::TimeDelta::FromMicroseconds(-1);
 }
 
+net::NextProto PseudoTcpAdapter::GetNegotiatedProtocol() const {
+  DCHECK(CalledOnValidThread());
+  return net::kProtoUnknown;
+}
+
 void PseudoTcpAdapter::SetAckDelay(int delay_ms) {
   DCHECK(CalledOnValidThread());
   core_->SetAckDelay(delay_ms);