Implements a focus manager for the extensions page.

chrome/browser/resources/extensions/extensions.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="../shared/js/cr/ui/drag_wrapper.js"></include>
 <include src="../uber/uber_utils.js"></include>
 <include src="extension_commands_overlay.js"></include>
+<include src="extension_focus_manager.js"></include>
 <include src="extension_list.js"></include>
 <include src="pack_extension_overlay.js"></include>
 
 // Used for observing function of the backend datasource for this page by
 // tests.
 var webui_responded_ = false;
 
 cr.define('extensions', function() {
   var ExtensionsList = options.ExtensionsList;
 
@@ skipping 88 matching lines @@
       var link = document.querySelector('.extension-commands-config');
       link.addEventListener('click',
           this.handleExtensionCommandsConfig_.bind(this));
 
       // Initialize the Commands overlay.
       var extensionCommandsOverlay =
           extensions.ExtensionCommandsOverlay.getInstance();
       extensionCommandsOverlay.initializePage();
 
       cr.ui.overlay.setupOverlay($('dropTargetOverlay'));
+
+      extensions.ExtensionFocusManager.getInstance().initialize();
     },
 
     /**
      * Handles the Load Unpacked Extension button.
      * @param {Event} e Change event.
      * @private
      */
     handleLoadUnpackedExtension_: function(e) {
       chrome.send('extensionSettingsLoadUnpackedExtension');
 
@@ skipping 126 matching lines @@
         loadTimeData.getString('cancel'),
         function() {
           chrome.send('pack', [crx_path, pem_path, overrideFlags]);
           closeAlert();
         },
         closeAlert);
     ExtensionSettings.showOverlay($('alertOverlay'));
   }
 
   /**
+   * Returns the current overlay or null if one does not exist.
+   * @return {Element} The overlay element.
+   */
+  ExtensionSettings.getCurrentOverlay = function() {
+    return document.querySelector('#overlay .page.showing');
+  }
+
+  /**
    * Sets the given overlay to show. This hides whatever overlay is currently
    * showing, if any.
    * @param {HTMLElement} node The overlay page to show. If falsey, all overlays
    *     are hidden.
    */
   ExtensionSettings.showOverlay = function(node) {
-    var currentlyShowingOverlay =
-        document.querySelector('#overlay .page.showing');
+    var currentlyShowingOverlay = ExtensionSettings.getCurrentOverlay();
     if (currentlyShowingOverlay)
       currentlyShowingOverlay.classList.remove('showing');
 
     if (node)
       node.classList.add('showing');
     overlay.hidden = !node;
     uber.invokeMethodOnParent(node ? 'beginInterceptingEvents' :
                                      'stopInterceptingEvents');
   }
 
@@ skipping 31 matching lines @@
   return {
     ExtensionSettings: ExtensionSettings
   };
 });
 
 var ExtensionSettings = extensions.ExtensionSettings;
 
 window.addEventListener('load', function(e) {
   ExtensionSettings.getInstance().initialize();
 });