The code responsible for creating the deletion form should live in DeleteAction, not in Article.
Rough plan:
- Move code from Article to DeleteAction, without changing anything: r712948
- Remove legacy code from Article after 1 train: r712975
- Make FileDeleteForm a subclass of DeleteAction, enabled via getActionOverrides(): r711477
- Clean up DeleteAction and FileDeleteForm: factor out common stuff, fix drifts, reduce differences in showForm: r711605, r711756, r712325, r712715, r712747, r713299, r713327,
r713338
[] Make DeleteAction a FormAction
Any further cleanup should be outside of the scope of this task.