options: Fix focus "Show advanced settings..." click focus regression.

chrome/browser/resources/options/browser_options.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.exportPath('options');
 
 /**
  * @typedef {{actionLinkText: (string|undefined),
  *            hasError: (boolean|undefined),
  *            hasUnrecoverableError: (boolean|undefined),
@@ skipping 98 matching lines @@
       }
 
       // Ensure that navigation events are unblocked on uber page. A reload of
       // the settings page while an overlay is open would otherwise leave uber
       // page in a blocked state, where tab switching is not possible.
       uber.invokeMethodOnParent('stopInterceptingEvents');
 
       window.addEventListener('message', this.handleWindowMessage_.bind(this));
 
       if (loadTimeData.getBoolean('allowAdvancedSettings')) {
-        $('advanced-settings-expander').onclick = function() {
+        $('advanced-settings-expander').onclick = function(e) {
           var showAdvanced =
               BrowserOptions.shouldShowSection_($('advanced-settings'));
           if (showAdvanced) {
             chrome.send('coreOptionsUserMetricsAction',
                         ['Options_ShowAdvancedSettings']);
           }
           self.toggleSectionWithAnimation_(
               $('advanced-settings'),
               $('advanced-settings-container'));
 
-          // If the link was focused (i.e., it was activated using the keyboard)
-          // and it was used to show the section (rather than hiding it), focus
-          // the first element in the container.
-          if (document.activeElement === $('advanced-settings-expander') &&

[Dan Beam, 2014/11/18 03:35:38]

mousedown can call .focus() so this wasn't particularly robust

-              showAdvanced) {
+          // If the click was triggered using the keyboard and it showed the
+          // section (rather than hiding it), focus the first element in the
+          // container.
+          if (!e.x && showAdvanced) {

[Dan Beam, 2014/11/18 03:35:37]

it's possible e.x != 0 in the future when pressing Enter
http://www.w3.org/TR/DOM-Level-3-Events/#click-synthesis

             var focusElement = $('advanced-settings-container').querySelector(
                 'button, input, list, select, a[href]');
             if (focusElement)
               focusElement.focus();
           }
         };
       } else {
         $('advanced-settings-expander').hidden = true;
         $('advanced-settings').hidden = true;
       }
@@ skipping 2029 matching lines @@
       }
       button.textContent = loadTimeData.getString(strId);
     };
   }
 
   // Export
   return {
     BrowserOptions: BrowserOptions
   };
 });