Mojo UDP socket: support connected mode.

mojo/services/network/public/cpp/udp_socket_wrapper.h

Index: mojo/services/network/public/cpp/udp_socket_wrapper.h
diff --git a/mojo/services/network/public/cpp/udp_socket_wrapper.h b/mojo/services/network/public/cpp/udp_socket_wrapper.h
index 32204d7cb3fe4764ab9115eccaa95ec62096575c..650f98e411cd5d1e21decd658e2188799f8fdf2c 100644
--- a/mojo/services/network/public/cpp/udp_socket_wrapper.h
+++ b/mojo/services/network/public/cpp/udp_socket_wrapper.h
@@ -43,6 +43,9 @@ class UDPSocketWrapper : public UDPSocketClient {
   void Bind(NetAddressPtr addr,
             const Callback<void(NetworkErrorPtr, NetAddressPtr)>& callback);
 
+  void Connect(NetAddressPtr remote_addr,
+               const Callback<void(NetworkErrorPtr, NetAddressPtr)>& callback);

[jamesr, 2015/01/22 00:32:37]

we really should generate typedefs for these callbacks..

[yzshen1, 2015/01/22 00:38:58]

Yeah. That should be pretty easy. I will put it in my TODO list. :)

+
   void SetSendBufferSize(uint32_t size, const ErrorCallback& callback);
 
   void SetReceiveBufferSize(uint32_t size, const ErrorCallback& callback);
@@ -51,10 +54,13 @@ class UDPSocketWrapper : public UDPSocketClient {
   // |callback| before it returns, and the return value is set to true.
   // Otherwise, the return value is set to false and the callback will be run
   // asynchronously.
+  // If the socket is connected, the net address pointer passed into the
+  // callback is set to null.
   bool ReceiveFrom(const ReceiveCallback& callback);
 
   // This method is aware of the max pending send requests allowed by the
   // service, and caches send requests locally if necessary.
+  // |dest_addr| is allowed to be null if the socket is connected.
   void SendTo(NetAddressPtr dest_addr,
               Array<uint8_t> data,
               const ErrorCallback& callback);