Refactor: make ESLint happy

Mock/addthis-com_addthis_widget.js

@@ -2,6 +2,7 @@
   'use strict';
 
   const noopfn = function () {
+    // noop
   };
   window.addthis = {
     addEventListener: noopfn,

Mock/www-google-analytics-com_cx_api.js

@@ -2,6 +2,7 @@
   'use strict';
 
   const noopfn = function () {
+    // noop
   };
   window.cxApi = {
     chooseVariation() {

Mock/www-google-analytics-com_inpage_linkid.js

@@ -3,6 +3,7 @@
 
   window._gaq = window._gaq || {
     push() {
+      // noop
     }
   };
 }());