Examine source code of Save Private Tabs

{
  "manifest_version": 2,
  "name": "Save Private Tabs",
  "version": "1.0",
  "description": "Save all your Private Windows.",
  "icons": {
    "48": "icons/border-48.png",
    "96": "icons/border-96.png"
  },
  "permissions": [
    "storage",
    "tabs"
  ],
  "browser_action": {
    "browser_style": true,
    "default_title": "Save Private Tabs",
    "default_popup": "tabs.html"
  }
}