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

webrtc/p2p/base/basicpacketsocketfactory.cc

Index: webrtc/p2p/base/basicpacketsocketfactory.cc
diff --git a/webrtc/p2p/base/basicpacketsocketfactory.cc b/webrtc/p2p/base/basicpacketsocketfactory.cc
index c478d6311202108bbaff642768508171aa1f9f06..22435753cbee1be7c3b091b5f7957903591c38b4 100644
--- a/webrtc/p2p/base/basicpacketsocketfactory.cc
+++ b/webrtc/p2p/base/basicpacketsocketfactory.cc
@@ -114,10 +114,16 @@ AsyncPacketSocket* BasicPacketSocketFactory::CreateClientTcpSocket(
   }
 
   if (BindSocket(socket, local_address, 0, 0) < 0) {
-    LOG(LS_ERROR) << "TCP bind failed with error "
-                  << socket->GetError();
-    delete socket;
-    return NULL;
+    // Allow BindSocket to fail if we're binding to the ANY address anyway. The

[pthatcher1, 2017/06/13 19:52:50]

Not sure what "anyway" adds to the end of the sentence.  It seems like you could
remove it.

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

Rephrased comment.

+    // socket will be bound when we call Connect() instead.
+    if (local_address.IsAnyIP()) {
+      LOG(LS_WARNING) << "TCP bind failed with error " << socket->GetError()
+                      << "; ignoring since socket is using 'any' address.";

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

Can you use an early return and then leave the rest of the code outside of the
else block?

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

I knew you would ask for an early return here. :)

And that's how I wrote the code originally, but it's notably less readable that
way; not worth removing a level of indentation imo.

+    } else {
+      LOG(LS_ERROR) << "TCP bind failed with error " << socket->GetError();
+      delete socket;
+      return NULL;
+    }
   }
 
   // If using a proxy, wrap the socket in a proxy socket.