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

chrome/browser/resources/extensions/pack_extension_overlay.js

 // Copyright (c) 2012 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.
 
 cr.define('extensions', function() {
   /**
    * PackExtensionOverlay class
    * Encapsulated handling of the 'Pack Extension' overlay page.
    * @constructor
    */
@@ skipping 42 matching lines @@
 
     /**
      * Utility function which asks the C++ to show a platform-specific file
      * select dialog, and fire |callback| with the |filePath| that resulted.
      * |selectType| can be either 'file' or 'folder'. |operation| can be 'load'
      * or 'pem' which are signals to the C++ to do some operation-specific
      * configuration.
      * @private
      */
     showFileDialog_: function(selectType, operation, callback) {
-      handleFilePathSelected = function(filePath) {
+      window.handleFilePathSelected = function(filePath) {
         callback(filePath);
-        handleFilePathSelected = function() {};
+        window.handleFilePathSelected = function() {};
       };
 
       chrome.send('packExtensionSelectFilePath', [selectType, operation]);
     },
 
     /**
      * Handles the showing of the extension directory browser.
      * @param {Event} e Change event.
      * @private
      */
@@ skipping 21 matching lines @@
    * @param {string} message The message to show to the user.
    */
   PackExtensionOverlay.showSuccessMessage = function(message) {
     alertOverlay.setValues(
         loadTimeData.getString('packExtensionOverlay'),
         message,
         loadTimeData.getString('ok'),
         '',
         function() {
           extensions.ExtensionSettings.showOverlay(null);
-        },
-        null);
+        });
     extensions.ExtensionSettings.showOverlay($('alertOverlay'));
   };
 
   /**
    * Post an alert overlay showing |message|, and upon acknowledgement, close
    * the alert overlay and return to showing the PackExtensionOverlay.
+   * @param {string} message The error message.
    */
   PackExtensionOverlay.showError = function(message) {
     alertOverlay.setValues(
         loadTimeData.getString('packExtensionErrorTitle'),
         message,
         loadTimeData.getString('ok'),
         '',
         function() {
           extensions.ExtensionSettings.showOverlay($('pack-extension-overlay'));
-        },
-        null);
+        });
     extensions.ExtensionSettings.showOverlay($('alertOverlay'));
   };
 
   // Export
   return {
     PackExtensionOverlay: PackExtensionOverlay
   };
 });