Add QJsonDocument::fromJson(QIODevice*, QJsonParseError *error = 0);

Currently creating QJsonObject instance from a network response is sub-optimal.

QNetworkReply is a QIODevice, but QJsonDocument accepts only QByteArray. Therefore code needs to construct a temporary array only for parsing. It looks like that:

QJsonObject data = QJsonDocument::fromJson(reply->readAll()).object();

I would prefer to not allocate space for json twice, especially that it may be big.