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

chrome/test/data/extensions/management/uninstall_extension/background.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.
 
 // The name of the extension to uninstall, from manifest.json.
 var EXPECTED_NAME = 'Auto-Update Test';
 
 chrome.management.getAll(function(items) {
   for (var i = 0; i < items.length; i++) {
     var item = items[i];
     if (item.name != EXPECTED_NAME) continue;
     var id = item.id;
     chrome.test.assertEq(false, item.mayDisable);
     chrome.management.uninstall(id, function() {
       // Check that the right error occured.
       var expectedError = 'Extension ' + id + ' cannot be modified by user';
-      chrome.test.assertEq(expectedError, chrome.extension.lastError.message);
+      chrome.test.assertEq(expectedError, chrome.runtime.lastError.message);
       chrome.test.sendMessage('ready');
     });
   }
 });