Move upgrader_process_complete from update-core.php to Core_Upgrader

[nacin]

upgrader_process_complete was placed in admin/includes/update-core.php because the subsequent hook, _core_updated_successfully, has a redirect set up. However, that redirect only occurs when you are updating from < 3.4. Thus, we don't care about whether the upgrader_process_complete fires, which we use for languages.

We can thus move it to Core_Upgrader, where it belongs, and for consistent with other Upgrader classes. It also, after the move, needs $this passed to it — again, for consistency with other Upgrader classes.

[nofearinc]

moving the upgrader_process_complete hook

[nofearinc]

Some proposal based on your request.

[nacin]

It needs to end up in Core_Upgrader::upgrade(), looks like that patch adds it to a theme upgrader class. But yeah, the gist is correct.

[dd32]

25659.2.diff​ should be all that's required here.

[nacin]

In 25861:

Move upgrader_process_complete for core to its proper place in Core_Upgrader.

This means it will be firing as a JS redirect is taking place if the update is from pre-3.4. Acceptable.

props dd32.
fixes #25659.