resolve_layout

# File actionpack/lib/action_view/renderer/template_renderer.rb, line 72
    def resolve_layout(layout, keys)
      case layout
      when String
        begin
          if layout =~ /^\//
            with_fallbacks { find_template(layout, nil, false, keys, @details) }
          else
            find_template(layout, nil, false, keys, @details)
          end
        rescue ActionView::MissingTemplate
          all_details = @details.merge(:formats => @lookup_context.default_formats)
          raise unless template_exists?(layout, nil, false, keys, all_details)
        end
      when Proc
        resolve_layout(layout.call, keys)
      when FalseClass
        nil
      else
        layout
      end
    end