Remove deprecated NonThreadSafe usage in net\socket.

net/socket/udp_socket_posix.h

Index: net/socket/udp_socket_posix.h
diff --git a/net/socket/udp_socket_posix.h b/net/socket/udp_socket_posix.h
index ba42e04430cac96328201d18557a543138939598..c4a3b56338111c39f5489de0469e9b0b58cfc345 100644
--- a/net/socket/udp_socket_posix.h
+++ b/net/socket/udp_socket_posix.h
@@ -12,7 +12,7 @@
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/message_loop/message_loop.h"
-#include "base/threading/non_thread_safe.h"
+#include "base/threading/thread_checker.h"
 #include "net/base/address_family.h"
 #include "net/base/completion_callback.h"
 #include "net/base/io_buffer.h"
@@ -31,7 +31,7 @@ class IPAddress;
 class NetLog;
 struct NetLogSource;
 
-class NET_EXPORT UDPSocketPosix : public base::NonThreadSafe {
+class NET_EXPORT UDPSocketPosix {
  public:
   UDPSocketPosix(DatagramSocket::BindType bind_type,
                  const RandIntCallback& rand_int_cb,
@@ -321,6 +321,8 @@ class NET_EXPORT UDPSocketPosix : public base::NonThreadSafe {
   // Network that this socket is bound to via BindToNetwork().
   NetworkChangeNotifier::NetworkHandle bound_network_;
 
+  THREAD_CHECKER(thread_checker_);
+
   DISALLOW_COPY_AND_ASSIGN(UDPSocketPosix);
 };