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

net/socket/socket_test_util.cc

Index: net/socket/socket_test_util.cc
diff --git a/net/socket/socket_test_util.cc b/net/socket/socket_test_util.cc
index 57cc3606c8b105f8a5a038a0e5c0062ba94fe626..ac17c793f47cfae24386133ada8c42c84e3c3d60 100644
--- a/net/socket/socket_test_util.cc
+++ b/net/socket/socket_test_util.cc
@@ -774,6 +774,10 @@ int MockClientSocket::SetSendBufferSize(int32_t size) {
   return OK;
 }
 
+int MockClientSocket::SetDoNotFragment(bool do_not_fragment) {
+  return OK;
+}
+
 void MockClientSocket::Disconnect() {
   connected_ = false;
 }
@@ -1336,6 +1340,10 @@ int MockUDPClientSocket::SetSendBufferSize(int32_t size) {
   return OK;
 }
 
+int MockUDPClientSocket::SetDoNotFragment(bool do_not_fragment) {
+  return OK;
+}
+
 void MockUDPClientSocket::Close() {
   connected_ = false;
 }