Examine source code of Free Time Calculator

{
  "update_url": "https://clients2.google.com/service/update2/crx",
  "manifest_version": 2,
  "name": "Free Time Calculator",
  "description": "A clean and simple calculator to calculate your free time, when you will be free.",
  "version": "1.0",
  "browser_action": {
    "default_icon": "icon128.png",
    "default_popup": "calculator.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{2404206f-a191-4b79-9349-52dff2b907ee}"
    }
  }
}