Re-use local variable instead of querySelector()ing it again

chrome/browser/resources/extensions/extension_error.js

 // Copyright 2013 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.define('extensions', function() {
   'use strict';
 
   /**
    * Clone a template within the extension error template collection.
    * @param {string} templateName The class name of the template to clone.
@@ skipping 96 matching lines @@
       var iconNode = document.createElement('img');
       iconNode.className = 'extension-error-icon';
       // TODO(hcarmona): Populate alt text with a proper description since this
       // icon conveys the severity of the error. (info, warning, fatal).
       iconNode.alt = '';
       this.insertBefore(iconNode, this.firstChild);
 
       var messageSpan = this.querySelector('.extension-error-message');
       messageSpan.textContent = error.message;
 
       var deleteButton = this.querySelector('.error-delete-button');

[Dan Beam, 2015/08/11 00:48:56]

^

       deleteButton.addEventListener('click', function(e) {
         this.dispatchEvent(
             new CustomEvent('deleteExtensionError',
                             {bubbles: true, detail: this.error}));
       }.bind(this));
 
       this.addEventListener('click', function(e) {
         if (e.target != deleteButton)
           this.requestActive_();
       }.bind(this));
       this.addEventListener('keydown', function(e) {
         if (e.keyIdentifier == 'Enter' && e.target != deleteButton)
           this.requestActive_();
       });
 
       this.addFocusableElement(this);
-      this.addFocusableElement(this.querySelector('.error-delete-button'));
+      this.addFocusableElement(deleteButton);

[hcarmona, 2015/08/11 01:39:35]

I'm curious how this behaves because |this| and |deleteButton| (a child
of |this|) are both added as focusable elements to the same row.

[Dan Beam, 2015/08/11 01:41:55]

Acknowledged.

     },
 
     /**
      * Bubble up an event to request to become active.
      * @private
      */
     requestActive_: function() {
       this.dispatchEvent(
           new CustomEvent('highlightExtensionError',
                           {bubbles: true, detail: this.error}));
@@ skipping 230 matching lines @@
     onFocus_: function() {
       var activeRow = this.gridBoundary_.querySelector('.focus-row-active');
       activeRow.getEquivalentElement(null).focus();
     },
   };
 
   return {
     ExtensionErrorList: ExtensionErrorList
   };
 });