Chrome extension: Navigate to a url when user clicks on icon

You can also navigate active tab to required url ( without opening new tab )

chrome.tabs.query( { active: true, currentWindow: true }, function( tabs ) {
  chrome.tabs.update( tabs[0].id, { url: "http://stackoverflow.com//" } ); 
});

You can use the following code:

chrome.tabs.update({
     url: "http://www.example.com/"
});

Use chrome.tabs.update({ url: "http://www.example.com/" }) in the onClicked listener of your browser action. When you omit the tabId argument, the update applies to the currently selected tab.

Despite being part of the chrome.tabs API, this does not require the tabs permission.