DO NOT MERGE YET: Fixes #3843, Action Bar: Secondary navigation tool?

- added an action provider that handles the long click and redirects to secondary default navigation

This would bring back the functionality as it was before, at the expense of loosing the normal long-press functionality.
No. Not at all. This ActionProvider has to call either the first or secondary navigation method. That behaviour does not change, if another activity is hosting the ActionProvider. Therefore having an interface would mean to implement exactly the same code in each of the interfaces implementations.

The activity object is only needed to invoke the new intent (and to be placed in the activity stack implicitly by that). There is no code which needs to be executed _by_ the activity.