Require manifests for native messaging hosts.

chrome/test/data/extensions/api_test/native_messaging/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.
 
-var appName = navigator.platform.match(/win/i) ? 'echo.bat' : 'echo.py';
+var appName = 'com.google.chrome.test.echo';
 
 chrome.test.getConfig(function(config) {
     chrome.test.runTests([
 
       function sendMessageWithCallback() {
         var message = {"text": "Hi there!", "number": 3};
         chrome.runtime.sendNativeMessage(
             appName, message,
             chrome.test.callbackPass(function(nativeResponse) {
           var expectedResponse = {"id": 1, "echo": message};
@@ skipping 25 matching lines @@
           currentMessage++;
 
           if (currentMessage == expectedResponses.length)
             chrome.test.notifyPass();
           else
             port.postMessage(messagesToSend[currentMessage]);
         });
       }
     ]);
 });