Only try to pair protocol matching candidates for creating connections.

webrtc/p2p/base/stunport.h

Index: webrtc/p2p/base/stunport.h
diff --git a/webrtc/p2p/base/stunport.h b/webrtc/p2p/base/stunport.h
index ccd3f36cc304678dba9e4120f737e1c319666b5b..ecf61a782dfc13ad2d3e64df48dbaa45c5c51324 100644
--- a/webrtc/p2p/base/stunport.h
+++ b/webrtc/p2p/base/stunport.h
@@ -95,6 +95,9 @@ class UDPPort : public Port {
     OnReadPacket(socket, data, size, remote_addr, packet_time);
     return true;
   }
+  virtual bool SupportsProtocol(const std::string& protocol) const {
+    return protocol == UDP_PROTOCOL_NAME;
+  }
 
   void set_stun_keepalive_delay(int delay) {
     stun_keepalive_delay_ = delay;