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

net/dns/mock_mdns_socket_factory.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef NET_DNS_MOCK_MDNS_SOCKET_FACTORY_H_
 #define NET_DNS_MOCK_MDNS_SOCKET_FACTORY_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 25 matching lines @@
              int buf_len,
              const IPEndPoint& address,
              const CompletionCallback& callback) override;
 
   MOCK_METHOD3(SendToInternal, int(const std::string& packet,
                                    const std::string address,
                                    const CompletionCallback& callback));
 
   MOCK_METHOD1(SetReceiveBufferSize, int(int32_t size));
   MOCK_METHOD1(SetSendBufferSize, int(int32_t size));
+  MOCK_METHOD0(SetDoNotFragment, int());
 
   MOCK_METHOD0(Close, void());
 
   MOCK_CONST_METHOD1(GetPeerAddress, int(IPEndPoint* address));
   int GetLocalAddress(IPEndPoint* address) const override;
   MOCK_CONST_METHOD0(NetLog, const BoundNetLog&());
 
   MOCK_METHOD0(AllowAddressReuse, void());
   MOCK_METHOD0(AllowBroadcast, void());
 
@@ skipping 48 matching lines @@
       std::vector<std::unique_ptr<DatagramServerSocket>>* sockets);
 
   scoped_refptr<IOBuffer> recv_buffer_;
   int recv_buffer_size_;
   CompletionCallback recv_callback_;
 };
 
 }  // namespace net
 
 #endif  // NET_DNS_MOCK_MDNS_SOCKET_FACTORY_H_