• When publishing a Talk message successfully based on a saved message, the user shouldn't land back on the Saved Messages activity, but rather back on the previous activity from which Saved Messages was invoked.
• When previewing a Talk message and pressing Back, it should always go back to editing the message. (it was doing this only in the case of arriving from the Diff screen)

This addresses all of the following:
https://phabricator.wikimedia.org/T358898#9671612
https://phabricator.wikimedia.org/T355141#9671572
https://phabricator.wikimedia.org/T356774#9671554