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

chrome/common/extensions/docs/examples/extensions/email_this_page/background.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.
 
 function customMailtoUrl() {
   if (window.localStorage == null)
     return "";
   if (window.localStorage.customMailtoUrl == null)
     return "";
   return window.localStorage.customMailtoUrl;
@@ skipping 24 matching lines @@
     console.log('Custom url: ' + action_url);
     chrome.tabs.create({ url: action_url });
   } else {
     // Plain vanilla mailto links open up in the same tab to prevent
     // blank tabs being left behind.
     console.log('Action url: ' + action_url);
     chrome.tabs.update(tab_id, { url: action_url });
   }
 }
 
-chrome.extension.onConnect.addListener(function(port) {
+chrome.runtime.onConnect.addListener(function(port) {
   var tab = port.sender.tab;
 
   // This will get called by the content script we execute in
   // the tab as a result of the user pressing the browser action.
   port.onMessage.addListener(function(info) {
     var max_length = 1024;
     if (info.selection.length > max_length)
       info.selection = info.selection.substring(0, max_length);
     executeMailto(tab.id, info.title, tab.url, info.selection);
   });
 });
 
 // Called when the user clicks on the browser action icon.
 chrome.browserAction.onClicked.addListener(function(tab) {
   // We can only inject scripts to find the title on pages loaded with http
   // and https so for all other pages, we don't ask for the title.
   if (tab.url.indexOf("http:") != 0 &&
       tab.url.indexOf("https:") != 0) {
     executeMailto(tab.id, "", tab.url, "");
   } else {
     chrome.tabs.executeScript(null, {file: "content_script.js"});
   }
 });