Add config to prune TURN ports

webrtc/p2p/base/relayport.h

Index: webrtc/p2p/base/relayport.h
diff --git a/webrtc/p2p/base/relayport.h b/webrtc/p2p/base/relayport.h
index 402736c34dbc1747f7992bca521c1256dfc7a68d..8fa2235043095e0d6a3158c0d461208ecb70ae0e 100644
--- a/webrtc/p2p/base/relayport.h
+++ b/webrtc/p2p/base/relayport.h
@@ -68,6 +68,12 @@ class RelayPort : public Port {
   const ProtocolAddress * ServerAddress(size_t index) const;
   bool IsReady() { return ready_; }
 
+  ProtocolType GetProtocol() const override {
+    // We shouldn't be using RelayPort, but we need to provide an
+    // implementation here.
+    return PROTO_UDP;
+  }
+
   // Used for testing.
   sigslot::signal1<const ProtocolAddress*> SignalConnectFailure;
   sigslot::signal1<const ProtocolAddress*> SignalSoftTimeout;