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

webrtc/base/firewallsocketserver.h

Index: webrtc/base/firewallsocketserver.h
diff --git a/webrtc/base/firewallsocketserver.h b/webrtc/base/firewallsocketserver.h
index 95ff039623a2800a8169cb2991f9c731958def2f..21a476b10b438205145819ce35f2884256b37f0f 100644
--- a/webrtc/base/firewallsocketserver.h
+++ b/webrtc/base/firewallsocketserver.h
@@ -58,6 +58,16 @@ class FirewallSocketServer : public SocketServer {
   bool Check(FirewallProtocol p,
              const SocketAddress& src, const SocketAddress& dst);
 
+  // Set the IP addresses for which Bind will fail. By default this list is
+  // empty. This can be used to simulate a real OS that refuses to bind to
+  // addresses under various circumstances.
+  //
+  // No matter how many addresses are added (including INADDR_ANY), the server
+  // will still allow creating outgoing TCP connections, since they don't
+  // require explicitly binding a socket.
+  void SetUnbindableIps(const std::vector<rtc::IPAddress>& unbindable_ips);
+  bool IsBindableIp(const rtc::IPAddress& ip);
+
   Socket* CreateSocket(int type) override;
   Socket* CreateSocket(int family, int type) override;
 
@@ -83,6 +93,7 @@ class FirewallSocketServer : public SocketServer {
     SocketAddress dst;
   };
   std::vector<Rule> rules_;
+  std::vector<rtc::IPAddress> unbindable_ips_;
   bool should_delete_server_;
   bool udp_sockets_enabled_;
   bool tcp_sockets_enabled_;