More closure fixes.

Author: Steven Orvell

lib/mixins/element-mixin.js

@@ -581,8 +581,9 @@ export const ElementMixin = dedupingMixin(base => {
      * Determines if a property dfeault can be applied. For example, this
      * prevents a default from being applied when a property that has no
      * accessor is overridden by its host before upgrade (e.g. via a binding).
+     * @override
      * @param {string} property Name of the property
-     * @returns {boolean} Returns true if the property default can be applied.
+     * @return {boolean} Returns true if the property default can be applied.
      */
     _canApplyPropertyDefault(property) {
       return !this.hasOwnProperty(property);