code: function() {
        var e$ = [];
        for (var i=0, l=elements.length, e; (i<l) && 
            (e=elements[i]); i++) {
          if (e.__queue && !e.__queue.flushable) {
            e$.push(e);
          }
        }
        return e$;
      }
docs: Returns a list of elements that have had polymer-elements created but
  are not yet ready to register. The list is an array of element definitions.