Adding PortAllocator option to support cases where sockets can't be bound.

webrtc/base/network.h

 /*
  *  Copyright 2004 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.
  */
 
@@ skipping 100 matching lines @@
   // include ignored networks.
   virtual void GetNetworks(NetworkList* networks) const = 0;
 
   // return the current permission state of GetNetworks()
   virtual EnumerationPermission enumeration_permission() const;
 
   // "AnyAddressNetwork" is a network which only contains single "any address"
   // IP address.  (i.e. INADDR_ANY for IPv4 or in6addr_any for IPv6). This is
   // useful as binding to such interfaces allow default routing behavior like
   // http traffic.
+  //
+  // This method appends the "any address" networks to the list, such that this
+  // can optionally be called after GetNetworks.

[Taylor Brandstetter, 2017/06/13 03:41:30]

Wanted to add this comment because I'm now starting to depend on the fact that
"GetNetworks" doesn't clear the list; I'm not sure if it was intentional
originally.

+  //
   // TODO(guoweis): remove this body when chromium implements this.
   virtual void GetAnyAddressNetworks(NetworkList* networks) {}
 
   // Dumps the current list of networks in the network manager.
   virtual void DumpNetworks() {}
   bool GetDefaultLocalAddress(int family, IPAddress* ipaddr) const override;
 
   struct Stats {
     int ipv4_network_count;
     int ipv6_network_count;
@@ skipping 290 matching lines @@
   int preference_;
   bool active_ = true;
   uint16_t id_ = 0;
 
   friend class NetworkManager;
 };
 
 }  // namespace rtc
 
 #endif  // WEBRTC_BASE_NETWORK_H_