Examine source code of session-resurrection pro

{
  "manifest_version": 2,
  "name": "session-resurrection",
  "version": "1.5",
  "description": "Save your browser sessions and reload them any time",
  "icons": {
    "48": "icons/sess-res-48.png"
  },
  "permissions": [
    "activeTab",
    "tabs",
    "storage",
    "<all_urls>",
    "webRequest"
  ],
  "browser_action": {
    "default_icon": "icons/sess-res-48.png",
    "default_title": "Session Resurrection",
    "default_popup": "/sessions-pop-up/index.html"
  },
  "background": {
    "scripts": [
      "/background.js"
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{c2197a9a-2058-4022-be09-1b5a930a65e8}"
    }
  }
}