The infobars API allows you to add horizontal panels to the top of tabs.

You implement the content of your infobar using HTML. Just like with other parts of the extension system, you can communicate to an from the infobar using APIs like chrome.extension.getBackgroundPage() and chrome.extension.getViews().

Infobars should be used to tell users something about a particular page. Google Chrome automatically closes an infobar when the page that it was displayed for is navigated elsewhere.

Manifest

Because the Infobars API is currently experimental, you must declare the "experimental" permission to use it. Also, you should specify a 16x16-pixel icon for display next to your infobar. For example:

{
  "name": "Andy's infobar extension",
  "version": "1.0",
  "permissions": ["experimental"],
  "icons": {
    "16": "16.png"
  },
  "background_page": "background.html"
}