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

chrome/common/extensions/docs/examples/api/eventPage/basic/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.
 
 // Global variables only exist for the life of the page, so they get reset
 // each time the page is unloaded.
 var counter = 1;
 
 var lastTabId = -1;
 function sendMessage() {
@@ skipping 38 matching lines @@
       // another here.
       sendMessage();
     });
   });
 });
 
 chrome.experimental.keybinding.onCommand.addListener(function(command) {
   chrome.tabs.create({url: "http://www.google.com/"});
 });
 
-chrome.extension.onMessage.addListener(function(msg, _, sendResponse) {
+chrome.runtime.onMessage.addListener(function(msg, _, sendResponse) {
   if (msg.setAlarm) {
     chrome.alarms.create({delayInMinutes: 0.1});
   } else if (msg.delayedResponse) {
     // Note: setTimeout itself does NOT keep the page awake. We return true
     // from the onMessage event handler, which keeps the message channel open -
     // in turn keeping the event page awake - until we call sendResponse.
     setTimeout(function() {
       sendResponse("Got your message.");
     }, 5000);
     return true;
@@ skipping 12 matching lines @@
 chrome.runtime.onSuspend.addListener(function() {
   chrome.tabs.query({active: true, currentWindow: true}, function(tabs) {
     // After the unload event listener runs, the page will unload, so any
     // asynchronous callbacks will not fire.
     alert("This does not show up.");
   });
   console.log("Unloading.");
   chrome.browserAction.setBadgeText({text: ""});
   chrome.tabs.sendMessage(lastTabId, "Background page unloaded.");
 });