Minimal Google Chrome browser extension

Manifest.json

{
    "name": "Extension Name",
    "version": "0.1",
    "manifest_version": 2,
    "browser_action": { },
    "permissions": [],
    "background": { "page": "background.html" }
}

background.html

<script src="background.js"></script>

background.js

chrome.browserAction.onClicked.addListener(function (tab) {
    alert('Hello World!');
});