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

chrome/common/extensions/docs/examples/extensions/ttsdemo/ttsdemo.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 text;
 var ttsStatus;
 var ttsStatusBox;
 var lang;
@@ skipping 68 matching lines @@
       chrome.tts.isSpeaking(function(isSpeaking) {
         if (!isSpeaking) {
           ttsStatus.innerHTML = 'Idle';
           ttsStatusBox.style.background = '#fff';
         }
       });
     }
   };
   chrome.tts.speak(
       str, options, function() {
-    if (chrome.extension.lastError) {
-      console.log('TTS Error: ' + chrome.extension.lastError.message);
+    if (chrome.runtime.lastError) {
+      console.log('TTS Error: ' + chrome.runtime.lastError.message);
     }
   });
   ttsStatus.innerHTML = 'Busy';
   ttsStatusBox.style.background = '#ffc';
 }
 
 function stop() {
   chrome.tts.stop();
 }
 
 function speakUserText() {
   var options = {};
   if (lang.value) {
     options.lang = lang.value;
   }
   speak(text.value, options, true);
 }
 
 document.addEventListener('DOMContentLoaded', load);