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..b9664f007ae00659aa45b119134d0a65dc64dfde 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 which can't be bound to using Bind. By default this

[pthatcher1, 2017/06/13 19:52:49]

"which can't be bound to using Bind" => "for which Bind will fail"?

[Taylor Brandstetter, 2017/06/13 22:11:17]

Done.

+  // 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 SetInvalidBindIps(const std::vector<rtc::IPAddress>& invalid_bind_ips);
+  bool CanBindToIp(const rtc::IPAddress& ip);

[pthatcher1, 2017/06/13 19:52:49]

Might make these symmetric: SetInvalidBindIps and IsInvalidBindIp.   

And I'd also suggest using the word "(un)bindable".  "SetUnbindableIps" and
"IsBindable" and unbindable_ips_.

[Taylor Brandstetter, 2017/06/13 22:11:17]

Done.

+
   Socket* CreateSocket(int type) override;
   Socket* CreateSocket(int family, int type) override;
 
@@ -83,6 +93,9 @@ class FirewallSocketServer : public SocketServer {
     SocketAddress dst;
   };
   std::vector<Rule> rules_;
+  // IP addresses which can't be successfully bound to, using Bind. If this
+  // list is empty, any address is accepted.

[pthatcher1, 2017/06/13 19:52:49]

You just need one comment to explain this, not two (here and in the Set method).
 One can reference the other.

[Taylor Brandstetter, 2017/06/13 22:11:17]

Done.

+  std::vector<rtc::IPAddress> invalid_bind_ips_;
   bool should_delete_server_;
   bool udp_sockets_enabled_;
   bool tcp_sockets_enabled_;