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

remoting/protocol/fake_session.cc

Index: remoting/protocol/fake_session.cc
diff --git a/remoting/protocol/fake_session.cc b/remoting/protocol/fake_session.cc
index 25f28847d115a704aa99152e97a40de353a7de31..44fbba896c92374fb7c1daf38074f9039abf4d4c 100644
--- a/remoting/protocol/fake_session.cc
+++ b/remoting/protocol/fake_session.cc
@@ -159,6 +159,11 @@ base::TimeDelta FakeSocket::GetConnectTimeMicros() const {
   return base::TimeDelta();
 }
 
+net::NextProto FakeSocket::GetNegotiatedProtocol() const {
+  NOTIMPLEMENTED();
+  return net::kProtoUnknown;
+}
+
 FakeUdpSocket::FakeUdpSocket()
     : read_pending_(false),
       input_pos_(0),