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

net/socket/ssl_server_socket_unittest.cc

Index: net/socket/ssl_server_socket_unittest.cc
diff --git a/net/socket/ssl_server_socket_unittest.cc b/net/socket/ssl_server_socket_unittest.cc
index e800cc6fd7621cbea4535c6757083d1d1a46c92a..b456b741c5f6c2820fa9dfaadfc57a4527ff39bf 100644
--- a/net/socket/ssl_server_socket_unittest.cc
+++ b/net/socket/ssl_server_socket_unittest.cc
@@ -194,6 +194,10 @@ class FakeSocket : public StreamSocket {
     return base::TimeDelta::FromMicroseconds(-1);
   }
 
+  virtual NextProto GetNegotiatedProtocol() const {
+    return kProtoUnknown;
+  }
+
  private:
   net::BoundNetLog net_log_;
   FakeDataChannel* incoming_;