Examine source code of Customize Background

{
  "manifest_version": 2,
  "name": "Customize Background",
  "version": "1.0",
  "description": "Customize Background the towering, snow-capped mountains, a lone warrior stands at the edge of a cliff",
  "icons": {
    "128": "icon128.png"
  },
  "permissions": [
    "geolocation"
  ],
  "chrome_url_overrides": {
    "newtab": "index.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{c5253555-2dd0-42c3-a939-f5dc18bf8ba1}"
    }
  }
}