The MCR update gives DifferenceEngine a new setRevisions() method which works like setContent() but can handle multiple slots. Callers that might need multi-slot should be updated to use it. At a glance, these are:
- EditPage::showDiff (view changes while editing; depends on multi-slot edit support)
- SpecialUndelete::showDiff ("diff" links on undelete page)
- TextConflictHelper::showEditFormTextAfterFooters (edit conflict)