Update references to the extension messaging APIs to point to the "runtime"

chrome/test/data/panels/context_menu/test.js

 // Copyright (c) 2012 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.
 
 function onclick(info) {
   chrome.test.sendMessage("clicked");
 }
 
 // Invoked by panel when it has loaded.
 function panelCallback() {
   chrome.contextMenus.create({"title":"Extension Item 1",
                               "onclick": onclick}, function() {
-    if (!chrome.extension.lastError) {
+    if (!chrome.runtime.lastError) {
       chrome.test.sendMessage("created item");
     }
   });
 }
 
 chrome.windows.create({'url': 'panel.html', 'type': 'panel'},
                       function() {});