lost feature (request) : download complete message holding its display position

Expected behavior

I split long messages to first downloaded partitially and read this then to the end. Below such a message there is then the button to 'download complete message'. Pressing this button should not move to the beginning of the message again, but the button should dismiss and one can continue reading there.

I'm nearly sure, that I've seen this feature working in one version of k-9.

Actual behavior

by loading the complete message the button geht's ghosted and the message again displays from beginning that one have to search, where it has ended before and where now to continue to read.

Steps to reproduce

1. have a long e-mail, which is loaded not complete (because of settings to do so)
2. scroll to end of message
3. submit to download complete message
   and finally find yourself on top of the message.

Environment

K-9 Mail version: 5.2.0.8

Android version: 4.2.2

Account type (IMAP, POP3, WebDAV/Exchange): IMAP, but not relevant IMHO

Start by reproducing the issue with a long partially downloaded IMAP message on the reported K-9 Mail 5.2.0.8 and Android 4.2.2 setup, then trace the entry point for downloading the complete message. Done means the download-complete action dismisses its button while keeping the reader at the previous scroll position instead of returning to the message start.