Rails will now use your default layout (such as "layouts/application") when you specify a layout with `:only` and `:except` condition, and those conditions fail.

For example, consider this snippet:

    class CarsController
      layout 'single_car', :only => :show
    end

Rails will use 'layouts/single_car' when a request comes in `:show` action, and use 'layouts/application' (or 'layouts/cars', if exists) when a request comes in for any other actions.