Revert of Removing references to webrtc::PortAllocatorFactoryInterface.

remoting/protocol/port_allocator_factory.h

-// Copyright 2015 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#ifndef REMOTING_PROTOCOL_PORT_ALLOCATOR_FACTORY_H_
-#define REMOTING_PROTOCOL_PORT_ALLOCATOR_FACTORY_H_
-
-#include "third_party/webrtc/p2p/base/portallocator.h"
-
-namespace remoting {
-namespace protocol {
-
-// Factory class used for creating cricket::PortAllocator that is used
-// for ICE negotiation.
-class PortAllocatorFactory {
- public:
-  virtual cricket::PortAllocator* CreatePortAllocator() = 0;
-
-  virtual ~PortAllocatorFactory() {}
-};
-
-}  // namespace protocol
-}  // namespace remoting
-
-#endif  // REMOTING_PROTOCOL_PORT_ALLOCATOR_FACTORY_H_