Examine source code of Foreground

{
  "manifest_version": 2,
  "name": "Foreground",
  "version": "0.1.1",
  "description": "Allows you to track the current active tab's URL in Foreground.",
  "browser_specific_settings": {
    "gecko": {
      "id": "addon@foreground.hellocode.co"
    }
  },
  "permissions": [
    "tabs"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": true
  }
}