MD Settings: Make up/down arrow work after closing the sidenav.

chrome/browser/resources/settings/settings_ui/settings_ui.js

 // Copyright 2015 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.
 
 /**
  * @fileoverview
  * 'settings-ui' implements the UI for the Settings page.
  *
  * Example:
  *
@@ skipping 246 matching lines @@
     if (event.detail.item.id != 'advancedSubmenu')
       this.$.drawer.closeDrawer();
   },
 
   /** @private */
   onMenuButtonTap_: function() {
     this.$.drawer.toggle();
   },
 
   /** @private */
+  onMenuClosed_: function() {
+    this.$$('settings-main').focus();
+  },
+
+  /** @private */
   directionDelegateChanged_: function() {
     this.$.drawer.align = this.directionDelegate.isRtl() ?
         'right' : 'left';
   },
 });