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

webrtc/base/natsocketfactory.cc

Index: webrtc/base/natsocketfactory.cc
diff --git a/webrtc/base/natsocketfactory.cc b/webrtc/base/natsocketfactory.cc
index d240527e4348fe2f74660de82d09375e96fb8c3c..95e64872199db3bf059614fcb8f8d7733e571e31 100644
--- a/webrtc/base/natsocketfactory.cc
+++ b/webrtc/base/natsocketfactory.cc
@@ -97,29 +97,20 @@ class NATSocket : public AsyncSocket, public sigslot::has_slots<> {
       return -1;
     }
 
-    int result;
-    socket_ = sf_->CreateInternalSocket(family_, type_, addr, &server_addr_);
-    result = (socket_) ? socket_->Bind(addr) : -1;
-    if (result >= 0) {
-      socket_->SignalConnectEvent.connect(this, &NATSocket::OnConnectEvent);
-      socket_->SignalReadEvent.connect(this, &NATSocket::OnReadEvent);
-      socket_->SignalWriteEvent.connect(this, &NATSocket::OnWriteEvent);
-      socket_->SignalCloseEvent.connect(this, &NATSocket::OnCloseEvent);
-    } else {
-      server_addr_.Clear();
-      delete socket_;
-      socket_ = nullptr;
-    }
-
-    return result;
+    return BindInternal(addr);
   }
 
   int Connect(const SocketAddress& addr) override {
-    if (!socket_) {  // socket must be bound, for now
-      return -1;
+    int result = 0;
+    // If we're not already bound (meaning |socket_| is null), bind to ANY
+    // address.
+    if (!socket_) {
+      result = BindInternal(SocketAddress(GetAnyIP(family_), 0));
+      if (result < 0) {
+        return result;
+      }
     }
 
-    int result = 0;
     if (type_ == SOCK_STREAM) {
       result = socket_->Connect(server_addr_.IsNil() ? addr : server_addr_);
     } else {
@@ -225,8 +216,16 @@ class NATSocket : public AsyncSocket, public sigslot::has_slots<> {
   AsyncSocket* Accept(SocketAddress* paddr) override {
     return socket_->Accept(paddr);
   }
-  int GetError() const override { return socket_->GetError(); }
-  void SetError(int error) override { socket_->SetError(error); }
+  int GetError() const override {
+    return socket_ ? socket_->GetError() : error_;
+  }
+  void SetError(int error) override {
+    if (socket_) {
+      socket_->SetError(error);
+    } else {
+      error_ = error;
+    }
+  }
   ConnState GetState() const override {
     return connected_ ? CS_CONNECTED : CS_CLOSED;
   }
@@ -266,6 +265,26 @@ class NATSocket : public AsyncSocket, public sigslot::has_slots<> {
   }
 
  private:
+  int BindInternal(const SocketAddress& addr) {
+    RTC_DCHECK(!socket_);
+
+    int result;
+    socket_ = sf_->CreateInternalSocket(family_, type_, addr, &server_addr_);
+    result = (socket_) ? socket_->Bind(addr) : -1;
+    if (result >= 0) {
+      socket_->SignalConnectEvent.connect(this, &NATSocket::OnConnectEvent);
+      socket_->SignalReadEvent.connect(this, &NATSocket::OnReadEvent);
+      socket_->SignalWriteEvent.connect(this, &NATSocket::OnWriteEvent);
+      socket_->SignalCloseEvent.connect(this, &NATSocket::OnCloseEvent);
+    } else {
+      server_addr_.Clear();
+      delete socket_;
+      socket_ = nullptr;
+    }
+
+    return result;
+  }
+
   // Makes sure the buffer is at least the given size.
   void Grow(size_t new_size) {
     if (size_ < new_size) {
@@ -302,6 +321,8 @@ class NATSocket : public AsyncSocket, public sigslot::has_slots<> {
   SocketAddress remote_addr_;
   SocketAddress server_addr_;  // address of the NAT server
   AsyncSocket* socket_;
+  // Need to hold error in case it occurs before the socket is created.
+  int error_ = 0;
   char* buf_;
   size_t size_;
 };