Fix 'chrome://settings/searchEngines' regression.

Fix for URL text selection regression in
'chrome://settings/searchEngines'.

BUG=427385

Review URL: https://codereview.chromium.org/682663002

Cr-Commit-Position: refs/heads/master@{#301421}

chrome/browser/resources/options/inline_editable_list.js

@@ -428,7 +428,9 @@ cr.define('options', function() {
       this.setAttribute('inlineeditable', '');
       this.addEventListener('hasElementFocusChange',
                             this.handleListFocusChange_);
-      this.removeAttribute('tabindex');
+      // <list> isn't focusable by default, but cr.ui.List defaults tabindex to
+      // 0 if it's not set.
+      this.tabIndex = -1;
     },
 
     /**