Ensure that sendMessage's callback is called.

chrome/test/data/extensions/api_test/messaging/connect_crash/test.js

 // Copyright 2015 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.
 
 chrome.runtime.onConnect.addListener(function(port) {
   var is_ready_to_crash = false;
   var succeed1 = chrome.test.callbackAdded();
   var succeed2 = chrome.test.callbackAdded();
 
   port.onMessage.addListener(function(msg) {
     chrome.test.assertEq('is_ready_to_crash', msg);
     is_ready_to_crash = true;
     chrome.test.sendMessage('ready_to_crash');
     // Now the browser test should kill the tab, and the port should be closed.
   });
   port.onDisconnect.addListener(function() {
     chrome.test.log('port.onDisconnect was triggered.');
     chrome.test.assertTrue(is_ready_to_crash);
     succeed1();
   });
 
   chrome.tabs.sendMessage(port.sender.tab.id, 'Rob says hi', function() {
     chrome.test.log('tab.sendMessage\'s response callback was invoked');
-    chrome.test.assertNoLastError();
+    chrome.test.assertLastError(
+        'The message port closed before a reponse was received.');
     succeed2();
   });
 });