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

net/http/http_proxy_client_socket.cc

Index: net/http/http_proxy_client_socket.cc
diff --git a/net/http/http_proxy_client_socket.cc b/net/http/http_proxy_client_socket.cc
index e99049e378793a49a6fe87c64683e881b92c1c93..d7b79ecb1013e6f5b13f0f080b827234a42f9bea 100644
--- a/net/http/http_proxy_client_socket.cc
+++ b/net/http/http_proxy_client_socket.cc
@@ -243,6 +243,10 @@ int HttpProxyClientSocket::SetSendBufferSize(int32_t size) {
   return transport_->socket()->SetSendBufferSize(size);
 }
 
+int HttpProxyClientSocket::SetDoNotFragment(bool do_not_fragment) {
+  return transport_->socket()->SetDoNotFragment(do_not_fragment);
+}
+
 int HttpProxyClientSocket::GetPeerAddress(IPEndPoint* address) const {
   return transport_->socket()->GetPeerAddress(address);
 }