Remove experimental permission from infobars API and moving it to dev channel

chrome/common/extensions/docs/examples/api/infobars/sandwichbar/background.js

 /**
  * Handles requests sent by the content script.  Shows an infobar.
  */
 function onRequest(request, sender, sendResponse) {
   // The number of matches is sent in the request - pass it to the
   // infobar.
   var url = "infobar.html#" + request.count;
 
   // Show the infobar on the tab where the request was sent.
-  chrome.experimental.infobars.show({
+  chrome.infobars.show({
     tabId: sender.tab.id,
     path: url
   });
 
   // Return nothing to let the connection be cleaned up.
   sendResponse({});
 };
 
 // Listen for the content script to send a message to the background page.
 chrome.extension.onRequest.addListener(onRequest);