Examine source code of Undo Closed Tabs Enhanced

{
  "manifest_version": 2,
  "name": "Undo Closed Tabs Enhanced",
  "version": "1.3",
  "description": "Restore recently closed tabs or windows with a click.",
  "permissions": [
    "sessions",
    "tabs"
  ],
  "browser_action": {
    "default_icon": "icons/logo_64.png",
    "default_title": "Undo Closed Tab",
    "default_popup": "popup.html"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "icons": {
    "32": "icons/logo_32.png",
    "64": "icons/logo_64.png",
    "128": "icons/logo_128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{362270f2-bf91-4fb9-b9cc-647efe6a8e1d}"
    }
  }
}