Examine source code of Notification Demo

{
  "name": "Notification Demo",
  "version": "1.1",
  "description": "Shows off desktop notifications, which are \"toast\" windows that pop up on the desktop.",
  "icons": {
    "16": "16.png",
    "48": "48.png",
    "128": "128.png"
  },
  "permissions": [
    "notifications"
  ],
  "options_page": "options.html",
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "manifest_version": 2,
  "web_accessible_resources": [
    "48.png"
  ]
}