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

net/http/http_proxy_client_socket_wrapper.cc

Index: net/http/http_proxy_client_socket_wrapper.cc
diff --git a/net/http/http_proxy_client_socket_wrapper.cc b/net/http/http_proxy_client_socket_wrapper.cc
index b857f0fef476cc23a9af48c77f8cdac8c89780b9..2dbc9ef8a0606fbdb2e956caf8bad8eb6f936e6f 100644
--- a/net/http/http_proxy_client_socket_wrapper.cc
+++ b/net/http/http_proxy_client_socket_wrapper.cc
@@ -303,6 +303,12 @@ int HttpProxyClientSocketWrapper::SetSendBufferSize(int32_t size) {
   return ERR_SOCKET_NOT_CONNECTED;
 }
 
+int HttpProxyClientSocketWrapper::SetDoNotFragment(bool do_not_fragment) {
+  if (transport_socket_)
+    return transport_socket_->SetDoNotFragment(do_not_fragment);
+  return ERR_SOCKET_NOT_CONNECTED;
+}
+
 int HttpProxyClientSocketWrapper::GetPeerAddress(IPEndPoint* address) const {
   if (transport_socket_)
     return transport_socket_->GetPeerAddress(address);