Add bind(), recvFrom(), sendTo() for UDP socket.

net/udp/udp_socket_libevent.h

Index: net/udp/udp_socket_libevent.h
diff --git a/net/udp/udp_socket_libevent.h b/net/udp/udp_socket_libevent.h
index 43177400fe78073dac1ffdff0ddf264c19cf2a35..cb0c938e60fa1e035a888402eb13d99b0d54aaf5 100644
--- a/net/udp/udp_socket_libevent.h
+++ b/net/udp/udp_socket_libevent.h
@@ -12,6 +12,7 @@
 #include "base/threading/non_thread_safe.h"
 #include "net/base/address_list_net_log_param.h"
 #include "net/base/completion_callback.h"
+#include "net/base/net_export.h"
 #include "net/base/rand_callback.h"
 #include "net/base/io_buffer.h"
 #include "net/base/ip_endpoint.h"
@@ -20,7 +21,7 @@
 
 namespace net {
 
-class UDPSocketLibevent : public base::NonThreadSafe {
+class NET_EXPORT UDPSocketLibevent : public base::NonThreadSafe {
  public:
   UDPSocketLibevent(DatagramSocket::BindType bind_type,
                     const RandIntCallback& rand_int_cb,