Examine source code of Restore Pages

{
  "manifest_version": 2,
  "name": "Restore Pages",
  "version": "1.0",
  "description": "Restores the last closed tab",
  "icons": {
    "48": "icon.png"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_icon": {
      "48": "icon.png"
    },
    "default_title": "Restore Pages"
  },
  "permissions": [
    "sessions"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{64a1cb97-f23e-4f40-bac8-6d23ed67fc0d}"
    }
  }
}