indexed_tabs/manifest.json

{
    "manifest_version": 2,

    "name": "Indexed Tabs",
    "description": "Shows tab numbers for fast switching",
    "version": "1.0",

    "permissions": [
        "tabs",
        "http://*/*",
        "https://*/*"
    ],

    "background": {
        "persistent": false,
        "scripts": ["background.js"]
    }
}