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

chrome/test/data/extensions/api_test/debugger/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 pass = chrome.test.callbackPass;
 var fail = chrome.test.callbackFail;
 
 var tabId;
 var debuggee;
 var protocolVersion = "1.0";
@@ skipping 30 matching lines @@
   },
 
   function attachAgain() {
     chrome.debugger.attach(debuggee, protocolVersion,
         fail("Another debugger is already attached to the tab with id: " +
                  tabId + "."));
   },
 
   function sendCommand() {
     function onResponse() {
-      if (chrome.extension.lastError &&
-          chrome.extension.lastError.message.indexOf("invalidMethod") != -1)
+      if (chrome.runtime.lastError &&
+          chrome.runtime.lastError.message.indexOf("invalidMethod") != -1)
         chrome.test.succeed();
       else
         chrome.test.fail();
     }
     chrome.debugger.sendCommand(debuggee,
                                "invalidMethod",
                                null,
                                onResponse);
   },
 
@@ skipping 31 matching lines @@
   function attachToWebUI() {
     chrome.tabs.create({url:"chrome://version"}, function(tab) {
       var debuggee = {tabId: tab.id};
       chrome.debugger.attach(debuggee, protocolVersion,
           fail("Can not attach to the page with the \"chrome://\" scheme."));
       chrome.tabs.remove(tab.id);
     });
   }
 
 ]);