Add closure types

Author: kevinpschaaf

lib/legacy/legacy-element-mixin.js

@@ -34,23 +34,31 @@ let styleInterface = window.ShadyCSS;
  * @polymer
  * @appliesMixin ElementMixin
  * @appliesMixin GestureEventListeners
+ * @appliesMixin DirMixin
  * @property isAttached {boolean} Set to `true` in this element's
  *   `connectedCallback` and `false` in `disconnectedCallback`
  * @summary Element class mixin that provides Polymer's "legacy" API
  */
 export const LegacyElementMixin = dedupingMixin((base) => {
 
+  // TODO(kschaaf): Note, the `@implements {Polymer_DirMixin}` is required here
+  // (rather than on legacyElementBase) for unknown reasons.
+  /**
+   * @constructor
+   * @implements {Polymer_ElementMixin}
+   * @implements {Polymer_GestureEventListeners}
+   * @implements {Polymer_DirMixin}
+   * @extends {HTMLElement}
+   * @private
+   */
   const GesturesElement = GestureEventListeners(ElementMixin(base));
 
   // Note, the DirMixin does nothing if css is built so avoid including it
   // in that case.
 
   /**
    * @constructor
-   * @implements {Polymer_ElementMixin}
-   * @implements {Polymer_GestureEventListeners}
-   * @implements {Polymer_DirMixin}
-   * @extends {HTMLElement}
+   * @extends {GesturesElement}
    * @private
    */
   const legacyElementBase = builtCSS ? GesturesElement :