cros: Add a11y to enable debugging screen.

chrome/browser/resources/chromeos/login/oobe_screen_enable_debugging.js

 // Copyright (c) 2014 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 Enable developer features screen implementation.
  */
 
 login.createScreen('EnableDebuggingScreen', 'debugging', function() {
   return {
@@ skipping 88 matching lines @@
     },
 
     /**
      * Returns a control which should receive an initial focus.
      */
     get defaultControl() {
       if (this.state_ == this.UI_STATE.REMOVE_PROTECTION)
         return $('debugging-remove-protection-button');
       else if (this.state_ == this.UI_STATE.SETUP)
         return $('enable-debugging-password');
-      else if (this.state_ == this.UI_STATE.DONE)
+      else if (this.state_ == this.UI_STATE.DONE ||
+               this.state_ == this.UI_STATE.ERROR) {
         return $('debugging-ok-button');
+      }
 
       return $('debugging-cancel-button');
     },
 
     /**
      * Cancels the enable debugging screen and drops the user back to the
      * network settings.
      */
     cancel: function() {
       chrome.send('enableDebuggingOnCancel');
@@ skipping 34 matching lines @@
 
       if (Oobe.getInstance().currentScreen === this)
         Oobe.getInstance().updateScreenSize(this);
     },
 
     updateState: function(state) {
       this.setDialogView_(state);
     }
   };
 });