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

chrome/browser/resources/extensions/extension_commands_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.
 
 <include src="extension_command_list.js">
 
 cr.define('extensions', function() {
   'use strict';
 
   // The Extension Commands list object that will be used to show the commands
@@ skipping 33 matching lines @@
      * @param {Event} e The click event.
      */
     handleDismiss_: function(e) {
       extensions.ExtensionSettings.showOverlay(null);
     },
   };
 
   /**
    * Called by the dom_ui_ to re-populate the page with data representing
    * the current state of extension commands.
+   * @param {!{commands: Array.<{name: string, id: string, commands: ?Array}>}}
+   *     extensionsData
    */
   ExtensionCommandsOverlay.returnExtensionsData = function(extensionsData) {
     ExtensionCommandList.prototype.data_ = extensionsData;
     var extensionCommandList = $('extension-command-list');
     ExtensionCommandList.decorate(extensionCommandList);
 
     // Make sure the config link is visible, since there are commands to show
     // and potentially configure.
     document.querySelector('.extension-commands-config').hidden =
         extensionsData.commands.length == 0;
 
     $('no-commands').hidden = extensionsData.commands.length > 0;
     var list = $('extension-command-list');
     if (extensionsData.commands.length == 0)
       list.classList.add('empty-extension-commands-list');
     else
       list.classList.remove('empty-extension-commands-list');
-  }
+  };
 
   // Export
   return {
     ExtensionCommandsOverlay: ExtensionCommandsOverlay
   };
 });