This is a recommit of

https://webrtc.googlesource.com/src.git/+/26246cac660a95f439b7d1c593edec2929806d3f
that was reverted due to compile error on windows.

Changes since last is an addition of a cast to uint16_t in stun.cc:1018.

---

Add RelayPortFactoryInterface that allows for custom relay (e.g turn) ports

This patch adds a RelayPortFactoryInterface that allows
for custom relay ports. The factor is added as optional argument
to BasicPortAlloctor. If none is provided a default implementation
that mimics existing behavior is created.

The patch also adds 2 stun functions, namely to copy a
StunAttribute and to remove StunAttribute's from a StunMessage.

Bug: webrtc:8640
Change-Id: If23638317130060286f576c94401de55c60a1821
Reviewed-on: https://webrtc-review.googlesource.com/34181
Reviewed-by: Guido Urdaneta <guidou@webrtc.org>
Reviewed-by: Peter Thatcher <pthatcher@webrtc.org>
Commit-Queue: Jonas Oreland <jonaso@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#21345}

p2p/client/relayportfactoryinterface.h

@@ -0,0 +1,72 @@
+/*
+ *  Copyright 2017 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef P2P_CLIENT_RELAYPORTFACTORYINTERFACE_H_
+#define P2P_CLIENT_RELAYPORTFACTORYINTERFACE_H_
+
+#include <memory>
+#include <string>
+
+#include "p2p/base/portinterface.h"
+#include "rtc_base/refcount.h"
+
+namespace rtc {
+class AsyncPacketSocket;
+class Network;
+class PacketSocketFactory;
+class Thread;
+}  // namespace rtc
+
+namespace webrtc {
+class TurnCustomizer;
+}  // namespace webrtc
+
+namespace cricket {
+class Port;
+struct ProtocolAddress;
+struct RelayServerConfig;
+
+// A struct containing arguments to RelayPortFactory::Create()
+struct CreateRelayPortArgs {
+  CreateRelayPortArgs();
+  rtc::Thread* network_thread;
+  rtc::PacketSocketFactory* socket_factory;
+  rtc::Network* network;
+  const ProtocolAddress* server_address;
+  const RelayServerConfig* config;
+  std::string username;
+  std::string password;
+  std::string origin;
+  webrtc::TurnCustomizer* turn_customizer;
+};
+
+inline CreateRelayPortArgs::CreateRelayPortArgs() {}
+
+// A factory for creating RelayPort's.
+class RelayPortFactoryInterface {
+ public:
+  virtual ~RelayPortFactoryInterface() {}
+
+  // This variant is used for UDP connection to the relay server
+  // using a already existing shared socket.
+  virtual std::unique_ptr<Port> Create(
+      const CreateRelayPortArgs& args,
+      rtc::AsyncPacketSocket* udp_socket) = 0;
+
+  // This variant is used for the other cases.
+  virtual std::unique_ptr<Port> Create(
+      const CreateRelayPortArgs& args,
+      int min_port,
+      int max_port) = 0;
+};
+
+}  // namespace cricket
+
+#endif  // P2P_CLIENT_RELAYPORTFACTORYINTERFACE_H_