Examine source code of Session Expiry Warning

{
  "manifest_version": 2,
  "name": "Session Expiry Warning",
  "version": "1.3",
  "description": "Notifies you before session cookies expire to help prevent unexpected logouts.",
  "permissions": [
    "cookies",
    "tabs",
    "notifications",
    "<all_urls>"
  ],
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": "icons/logo_64.png"
  },
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "icons": {
    "32": "icons/logo_32.png",
    "64": "icons/logo_64.png",
    "128": "icons/logo_128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{3964edea-445d-4405-9295-ac8c5070b0f6}"
    }
  }
}