Make Port (and subclasses) fully "Network"-based, instead of IP-based.

webrtc/rtc_base/virtualsocketserver.h

Index: webrtc/rtc_base/virtualsocketserver.h
diff --git a/webrtc/rtc_base/virtualsocketserver.h b/webrtc/rtc_base/virtualsocketserver.h
index a08bc0ce389829f0f24fac01c3feff50c648cee2..089e73a13d09cdb9682291656fd727895c4b7d07 100644
--- a/webrtc/rtc_base/virtualsocketserver.h
+++ b/webrtc/rtc_base/virtualsocketserver.h
@@ -118,6 +118,16 @@ class VirtualSocketServer : public SocketServer, public sigslot::has_slots<> {
     delay_by_ip_[address.ipaddr()] = delay_ms;
   }
 
+  // Used by TurnPortTest and TcpPortTest (for example), to mimic a case where
+  // a proxy returns the local host address instead of the original one the
+  // port was bound against. Please see WebRTC issue 3927 for more detail.
+  //
+  // If SetAlternativeLocalAddress(A, B) is called, then when something
+  // attempts to bind a socket to address A, it will get a socket bound to
+  // address B instead.
+  void SetAlternativeLocalAddress(const rtc::IPAddress& address,
+                                  const rtc::IPAddress& alternative);
+
   typedef std::pair<double, double> Point;
   typedef std::vector<Point> Function;
 
@@ -273,6 +283,7 @@ class VirtualSocketServer : public SocketServer, public sigslot::has_slots<> {
   uint32_t delay_samples_;
 
   std::map<rtc::IPAddress, int> delay_by_ip_;
+  std::map<rtc::IPAddress, rtc::IPAddress> alternative_address_mapping_;
   std::unique_ptr<Function> delay_dist_;
 
   CriticalSection delay_crit_;
@@ -294,11 +305,6 @@ class VirtualSocket : public AsyncSocket,
   SocketAddress GetLocalAddress() const override;
   SocketAddress GetRemoteAddress() const override;
 
-  // Used by TurnPortTest to mimic a case where proxy returns local host address
-  // instead of the original one TurnPort was bound against. Please see WebRTC
-  // issue 3927 for more detail.
-  void SetAlternativeLocalAddress(const SocketAddress& addr);
-
   int Bind(const SocketAddress& addr) override;
   int Connect(const SocketAddress& addr) override;
   int Close() override;
@@ -353,7 +359,6 @@ class VirtualSocket : public AsyncSocket,
   ConnState state_;
   int error_;
   SocketAddress local_addr_;
-  SocketAddress alternative_local_addr_;
   SocketAddress remote_addr_;
 
   // Pending sockets which can be Accepted