Examine source code of Private Tab History

{
  "manifest_version": 2,
  "name": "Private Tab History",
  "version": "1.0",
  "description": "Stores browsing history for private/incognito tabs.",
  "permissions": [
    "activeTab",
    "storage",
    "tabs",
    "<all_urls>"
  ],
  "incognito": "spanning",
  "browser_action": {
    "default_popup": "popup.html"
  },
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": true
  },
  "icons": {
    "48": "icon.png",
    "128": "icon.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{b66c094f-1d4f-4218-a17f-6c0da9d62bb6}"
    }
  }
}