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

chrome/common/extensions/docs/examples/api/messaging/timer/page.js

-chrome.extension.onConnect.addListener(function(port) {
+chrome.runtime.onConnect.addListener(function(port) {
   port.onMessage.addListener(function(msg) {
     port.postMessage({counter: msg.counter+1});
   });
 });
 
 chrome.extension.onRequest.addListener(
   function(request, sender, sendResponse) {
     sendResponse({counter: request.counter+1});
   });