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

chrome/common/extensions/docs/examples/extensions/native_messaging/popup.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 port = null;
 
 function gotNativeMessage(message) {
   document.getElementById('response').innerHTML = "<p>Message Number: " +
                                                   message.id +
                                                   "</p><p>Message Text: " +
                                                   JSON.stringify(message.echo) +
                                                   "</p>";
 }
 
 function sendNativeMessage() {
   if (!port) {
-    port = chrome.extension.connectNative('echo.py', {"message": "Hi there!"});
+    port = chrome.runtime.connectNative('echo.py', {"message": "Hi there!"});
     port.onMessage.addListener(gotNativeMessage);
     document.getElementById('input-text').style.display = 'block';
     document.getElementById('send-native-message').innerHTML = 'Send Message';
   } else {
     port.postMessage({"message": document.getElementById('input-text').value});
   }
 }
 
 document.addEventListener('DOMContentLoaded', function () {
   document.getElementById('input-text').style.display = 'none';
   document.getElementById('send-native-message').addEventListener(
       'click', sendNativeMessage);
 });