I am using Google Chrome dev. currently on version 22, it seems as if Google is testing new UI dialog to make Gmail as default handler to open email links and seems the process is unfinished and this feature is live when you visit Gmail sign-in page in your browser, at top right-side of the omnibox you can spot black and light blue icon.

When you hover the  mouse pointer on it, it shows “this page wants to install a service handler” when you click on it a pop-up appears do you “allow Gmail (mail.google.com) to open all email links” with options as use Gmail, No, Ignore and Manager Handler settings link at the bottom.

service handler notification icon in Chrome omnibox

Update : Read How to Disable Service/Site Handler Requests in Google Chrome

Gmail’s Service Handler icon in Chrome doesn’t goes away

The annoying part is this icon doesn’t go away if you select any one of the option said above and that’s strange. Protocol Handlers dialog which appears when you click on “Manager handler setting”s hasn’t either. After searching in Google, we came to know that it’s Chromium team’s plan to Change permission-granting UI for RegisterProtocolHandler.

service handler popup dialog for Gmail