Move UseNonBlockingIO from a windows-only method

net/udp/datagram_socket.h

Index: net/udp/datagram_socket.h
diff --git a/net/udp/datagram_socket.h b/net/udp/datagram_socket.h
index f0e9fa10baa7fb181b9b2cc6810459c6c31359d6..b61e831bdf499ca93be031049d162db36bda1609 100644
--- a/net/udp/datagram_socket.h
+++ b/net/udp/datagram_socket.h
@@ -34,6 +34,10 @@ class NET_EXPORT_PRIVATE DatagramSocket {
   // (similar to getsockname)
   virtual int GetLocalAddress(IPEndPoint* address) const = 0;
 
+  // Switch to use non-blocking IO. Must be called right after construction and
+  // before other calls.
+  virtual void UseNonBlockingIO() = 0;
+
   // Gets the NetLog for this socket.
   virtual const BoundNetLog& NetLog() const = 0;
 };