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

chrome/test/data/extensions/api_test/content_scripts/bypass_page_csp/a.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.
 
 // Inject an image.
 var img = document.createElement('img');
 img.onload = function () {
-  chrome.extension.connect().postMessage(true);
+  chrome.runtime.connect().postMessage(true);
 };
 img.onerror = function () {
-  chrome.extension.connect().postMessage(false);
+  chrome.runtime.connect().postMessage(false);
 };
 img.src = 'icon3.png';
 document.body.appendChild(img);