Revert of Revert "Typecheck JS files for chrome://extensions"

chrome/browser/resources/extensions/extension_error.js

Index: chrome/browser/resources/extensions/extension_error.js
diff --git a/chrome/browser/resources/extensions/extension_error.js b/chrome/browser/resources/extensions/extension_error.js
index 28f3dc4832e1cf1741fa9b74bb130542efb1c31a..107da28daf1de8f1d5e7b91de93f2e598bac1dc0 100644
--- a/chrome/browser/resources/extensions/extension_error.js
+++ b/chrome/browser/resources/extensions/extension_error.js
@@ -1,8 +1,6 @@
 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
-
-<include src="extension_error_overlay.js">
 
 cr.define('extensions', function() {
   'use strict';
@@ -13,8 +11,8 @@
    * @return {HTMLElement} The clone of the template.
    */
   function cloneTemplate(templateName) {
-    return $('template-collection-extension-error').
-        querySelector('.' + templateName).cloneNode(true);
+    return /** @type {HTMLElement} */($('template-collection-extension-error').
+        querySelector('.' + templateName).cloneNode(true));
   }
 
   /**
@@ -44,7 +42,10 @@
   ExtensionError.prototype = {
     __proto__: HTMLDivElement.prototype,
 
-    /** @override */
+    /**
+     * @param {RuntimeError} error
+     * @override
+     */
     decorate: function(error) {
       // Add an additional class for the severity level.
       if (error.level == 0)