Examine source code of Sparkle Backgrounds

{
  "manifest_version": 2,
  "name": "Sparkle Random Backgrounds",
  "version": "1.0",
  "description": "Automatically change wallpaper every time you open a new tab.",
  "chrome_url_overrides": {
    "newtab": "newtab.html"
  },
  "permissions": [],
  "web_accessible_resources": [
    "background/*"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{352a4af1-843f-4ab6-bfea-4109c41450a8}"
    }
  }
}