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

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 b61e831bdf499ca93be031049d162db36bda1609..19936979f4157706bdf3f1a5a2505e8d7edba0ed 100644
--- a/net/udp/datagram_socket.h
+++ b/net/udp/datagram_socket.h
@@ -38,6 +38,13 @@ class NET_EXPORT_PRIVATE DatagramSocket {
   // before other calls.
   virtual void UseNonBlockingIO() = 0;
 
+  // Requests that packets sent by this socket not be fragment, either locally
+  // by the host, or by routers (via the DF bit in the IPv4 packet header).
+  // May not be supported by all platforms. Returns a return a network error
+  // code if there was a problem, but the socket will still be usable. Can not
+  // return ERR_IO_PENDING.
+  virtual int SetDoNotFragment() = 0;
+
   // Gets the NetLog for this socket.
   virtual const BoundNetLog& NetLog() const = 0;
 };