# File lib/action_view/helpers/asset_tag_helper.rb, line 532
          def initialize(template, controller, source, include_host = true)
            # NOTE: The template arg is temporarily needed for a legacy plugin
            # hook that is expected to call rewrite_asset_path on the
            # template. This should eventually be removed.
            @template = template
            @controller = controller
            @source = source
            @include_host = include_host
            @cache_key = if controller.respond_to?(:request)
              [self.class.name,controller.request.protocol,
               ActionController::Base.asset_host,
               ActionController::Base.relative_url_root,
               source, include_host]
            else
              [self.class.name,ActionController::Base.asset_host, source, include_host]
            end
          end