Make toggleAttribute match with native signature (#5372)

Author: 43081j

lib/legacy/legacy-element-mixin.js

@@ -816,11 +816,13 @@ export const LegacyElementMixin = dedupingMixin((base) => {
      * @param {string} name HTML attribute name
      * @param {boolean=} bool Boolean to force the attribute on or off.
      *    When unspecified, the state of the attribute will be reversed.
-     * @param {Element=} node Node to target.  Defaults to `this`.
      * @return {boolean} true if the attribute now exists
      */
-    toggleAttribute(name, bool, node) {
-      node = /** @type {Element} */ (node || this);
+    toggleAttribute(name, bool) {
+      let node = /** @type {Element} */ this;
+      if (arguments.length === 3) {
+        node = /** @type {Element} */ arguments[2];
+      }
       if (arguments.length == 1) {
         bool = !node.hasAttribute(name);
       }