QNetworkProxy::HttpProxy eat memory on PUT

I noticed that sending a big file with :

QNetworkReply *QNetworkAccessManager::put(const QNetworkRequest &request, QIODevice *data)

eat a lot of memory increasingly during upload (very noticeable on big files) and does not free it after.

Attached a sample project. Just :

• Fill an URL where to PUT the file (no need to have an http server really accepting the PUT command to notice the bug)

• Check proxy group and fill hostname and port (the one per default is valid as time of writing)

• Click on "upload" button to choose a big file (quickly done, avoid file where size > 2^32 bytes if you want to see progress bar, few hundreds megabytes file is quite enough)

• Notice the RAM consumption in Windows task manager

If you do a similar upload without the proxy, memory stay stable.