Add a SetDoNotFragment() method to DatagramSocket, and call this for

net/udp/udp_socket_posix.h

Index: net/udp/udp_socket_posix.h
diff --git a/net/udp/udp_socket_posix.h b/net/udp/udp_socket_posix.h
index 305c435334ae0c4f27de4f29b72b66671a92207a..148efc4973d6ea997fa029bde8b0dfe426d42158 100644
--- a/net/udp/udp_socket_posix.h
+++ b/net/udp/udp_socket_posix.h
@@ -119,6 +119,10 @@ class NET_EXPORT UDPSocketPosix : public base::NonThreadSafe {
   // Returns a net error code.
   int SetSendBufferSize(int32_t size);
 
+  // Configures the socket to set or clear the DF (Do not Fragment) bit on
+  // packets, which prevents routers from fragmenting them.
+  int SetDoNotFragment(bool do_not_fragment);
+
   // Returns true if the socket is already connected or bound.
   bool is_connected() const { return is_connected_; }