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

chrome/common/extensions/docs/examples/api/debugger/pause-resume/background.js

 // Copyright (c) 2011 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 attachedTabs = {};
 var version = "1.0";
 
 chrome.debugger.onEvent.addListener(onEvent);
 chrome.debugger.onDetach.addListener(onDetach);
 
@@ skipping 10 matching lines @@
   if (attachedTabs[tabId] == "pausing")
     return;
 
   if (!attachedTabs[tabId])
     chrome.debugger.attach(debuggeeId, version, onAttach.bind(null, debuggeeId));
   else if (attachedTabs[tabId])
     chrome.debugger.detach(debuggeeId, onDetach.bind(null, debuggeeId));
 }
 
 function onAttach(debuggeeId) {
-  if (chrome.extension.lastError) {
-    alert(chrome.extension.lastError.message);
+  if (chrome.runtime.lastError) {
+    alert(chrome.runtime.lastError.message);
     return;
   }
 
   var tabId = debuggeeId.tabId;
   chrome.browserAction.setIcon({tabId: tabId, path:"debuggerPausing.png"});
   chrome.browserAction.setTitle({tabId: tabId, title:"Pausing JavaScript"});
   attachedTabs[tabId] = "pausing";
   chrome.debugger.sendCommand(
       debuggeeId, "Debugger.enable", {},
       onDebuggerEnabled.bind(null, debuggeeId));
@@ skipping 11 matching lines @@
     chrome.browserAction.setTitle({tabId:tabId, title:"Resume JavaScript"});
   }
 }
 
 function onDetach(debuggeeId) {
   var tabId = debuggeeId.tabId;
   delete attachedTabs[tabId];
   chrome.browserAction.setIcon({tabId:tabId, path:"debuggerPause.png"});
   chrome.browserAction.setTitle({tabId:tabId, title:"Pause JavaScript"});
 }