Modify devices page to match the latest mocks

chrome/test/data/webui/local_discovery_ui_test.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.
 
 var $ = document.getElementById.bind(document);
 
 function checkOneDevice() {
-  var devices = $('registered-devices').children;
+  var devices = $('register-device-list').children;
   assertEquals(1, devices.length);
   var firstDevice = devices[0];
 
   var deviceName = firstDevice.querySelector('.device-name').textContent;
   assertEquals('Sample device', deviceName);
 
   var deviceDescription =
         firstDevice.querySelector('.device-description').textContent;
   assertEquals('Sample device description', deviceDescription);
 
   var button = firstDevice.querySelector('button');
   assertEquals(true, button.disabled);
 }
 
 function checkNoDevices() {
-  assertEquals(0, $('unregistered-devices').children.length);
-  assertEquals(0, $('registered-devices').children.length);
+  assertEquals(0, $('register-device-list').children.length);
 }