Bind a socket to a network if the network handle is set.

webrtc/base/natsocketfactory.cc

Index: webrtc/base/natsocketfactory.cc
diff --git a/webrtc/base/natsocketfactory.cc b/webrtc/base/natsocketfactory.cc
index 0abd2a1b056d80b600a667cabbb59b4637e0a2e8..7820deaa9ee36e38aabf070bdf752f10e7792bed 100644
--- a/webrtc/base/natsocketfactory.cc
+++ b/webrtc/base/natsocketfactory.cc
@@ -109,6 +109,8 @@ class NATSocket : public AsyncSocket, public sigslot::has_slots<> {
     return result;
   }
 
+  int BindToNetwork(NetworkHandle net_handle) override { return 0; }
+
   int Connect(const SocketAddress& addr) override {
     if (!socket_) {  // socket must be bound, for now
       return -1;