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

webrtc/base/socketserver.h

Index: webrtc/base/socketserver.h
diff --git a/webrtc/base/socketserver.h b/webrtc/base/socketserver.h
index 15c56f4612798e5c2bcba3972d664ce774c84cde..1b4136d74e3246010ac770f13d5baf2337bc8307 100644
--- a/webrtc/base/socketserver.h
+++ b/webrtc/base/socketserver.h
@@ -16,6 +16,7 @@
 namespace rtc {
 
 class MessageQueue;
+class NetworkBinderInterface;
 
 // Provides the ability to wait for activity on a set of sockets.  The Thread
 // class provides a nice wrapper on a socket server.
@@ -39,6 +40,16 @@ class SocketServer : public SocketFactory {
 
   // Causes the current wait (if one is in progress) to wake up.
   virtual void WakeUp() = 0;
+
+  // A network binder will bind the created sockets to a network.
+  // It is only used in PhysicalSocketServer.
+  void set_network_binder(NetworkBinderInterface* binder) {
+    network_binder_ = binder;
+  }
+  NetworkBinderInterface* network_binder() const { return network_binder_; }
+
+ private:
+  NetworkBinderInterface* network_binder_ = nullptr;
 };
 
 }  // namespace rtc