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

net/socket/socket_test_util.cc

 // Copyright (c) 2012 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.
 
 #include "net/socket/socket_test_util.h"
 
 #include <algorithm>
 #include <utility>
 #include <vector>
 
@@ skipping 1313 matching lines @@
 }
 
 int MockUDPClientSocket::SetReceiveBufferSize(int32_t size) {
   return OK;
 }
 
 int MockUDPClientSocket::SetSendBufferSize(int32_t size) {
   return OK;
 }
 
+int MockUDPClientSocket::SetDoNotFragment() {
+  return OK;
+}
+
 void MockUDPClientSocket::Close() {
   connected_ = false;
 }
 
 int MockUDPClientSocket::GetPeerAddress(IPEndPoint* address) const {
   *address = peer_addr_;
   return OK;
 }
 
 int MockUDPClientSocket::GetLocalAddress(IPEndPoint* address) const {
@@ skipping 381 matching lines @@
 }
 
 int64_t CountWriteBytes(const MockWrite writes[], size_t writes_size) {
   int64_t total = 0;
   for (const MockWrite* write = writes; write != writes + writes_size; ++write)
     total += write->data_len;
   return total;
 }
 
 }  // namespace net