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

remoting/protocol/pepper_transport_socket_adapter.cc

Index: remoting/protocol/pepper_transport_socket_adapter.cc
diff --git a/remoting/protocol/pepper_transport_socket_adapter.cc b/remoting/protocol/pepper_transport_socket_adapter.cc
index b0067436d16493988462a725b44fa8ff6e720017..e4e47d551560536d9bdee844d0b410f98c3deb8f 100644
--- a/remoting/protocol/pepper_transport_socket_adapter.cc
+++ b/remoting/protocol/pepper_transport_socket_adapter.cc
@@ -219,6 +219,11 @@ base::TimeDelta PepperTransportSocketAdapter::GetConnectTimeMicros() const {
   return base::TimeDelta();
 }
 
+net::NextProto PepperTransportSocketAdapter::GetNegotiatedProtocol() const {
+  DCHECK(CalledOnValidThread());
+  NOTIMPLEMENTED();
+  return net::kProtoUnknown;
+}
 
 int PepperTransportSocketAdapter::ProcessCandidates() {
   DCHECK(CalledOnValidThread());