Deleted unused method EstimateMTU, and the WinPing class.

webrtc/base/natsocketfactory.cc

Index: webrtc/base/natsocketfactory.cc
diff --git a/webrtc/base/natsocketfactory.cc b/webrtc/base/natsocketfactory.cc
index 7aa6838e17e517d2b657f4de9e67561a675e74b6..67172fb50db451fd2af0d903714dbce3fd3488e1 100644
--- a/webrtc/base/natsocketfactory.cc
+++ b/webrtc/base/natsocketfactory.cc
@@ -230,7 +230,6 @@ class NATSocket : public AsyncSocket, public sigslot::has_slots<> {
   ConnState GetState() const override {
     return connected_ ? CS_CONNECTED : CS_CLOSED;
   }
-  int EstimateMTU(uint16_t* mtu) override { return socket_->EstimateMTU(mtu); }
   int GetOption(Option opt, int* value) override {
     return socket_->GetOption(opt, value);
   }