Debug the filter chain of a controller

FooController._process_action_callbacks.map(&:filter)
#=> [:handle_password_change, :activate_draper, ...]

Or a bit more detailed:

FooController._process_action_callbacks.map { |c| [c.kind, c.filter] }
#=> [[:before, :handle_password_change], [:before, :activate_draper], ...]