Fix some lingering WebUI focus issues.

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="../../../../ui/webui/resources/js/cr/ui/focus_row.js">
 <include src="../../../../ui/webui/resources/js/cr/ui/focus_grid.js">
 <include src="../uber/uber_utils.js">
 <include src="extension_code.js">
 <include src="extension_commands_overlay.js">
 <include src="extension_error_overlay.js">
@@ skipping 368 matching lines @@
     document.body.classList.toggle('no-scroll', !!node);
 
     var currentlyShowingOverlay = ExtensionSettings.getCurrentOverlay();
     if (currentlyShowingOverlay) {
       if (currentlyShowingOverlay == node)  // Already displayed.
         return;
       currentlyShowingOverlay.classList.remove('showing');
     }
 
     if (node) {
-      var lastFocused = document.activeElement;
+      var lastFocused;
+
+      var focusOutlineManager = cr.ui.FocusOutlineManager.forDocument(document);
+      if (focusOutlineManager.visible)
+        lastFocused = document.activeElement;
+
       $('overlay').addEventListener('cancelOverlay', function f() {
-        lastFocused.focus();
+        if (lastFocused && focusOutlineManager.visible)
+          lastFocused.focus();
+
         $('overlay').removeEventListener('cancelOverlay', f);
       });
       node.classList.add('showing');
     }
 
     var pages = document.querySelectorAll('.page');
     for (var i = 0; i < pages.length; i++) {
       pages[i].setAttribute('aria-hidden', node ? 'true' : 'false');
     }
 
@@ skipping 62 matching lines @@
   // Export
   return {
     ExtensionSettings: ExtensionSettings
   };
 });
 
 window.addEventListener('load', function(e) {
   document.documentElement.classList.add('loading');
   extensions.ExtensionSettings.getInstance().initialize();
 });