Examine source code of LastModifiedInfo

{
  "description": "Notify Last Modified Date & time of web page.Get the date from http protocol sended by web server.",
  "manifest_version": 2,
  "name": "LastModified",
  "version": "1.1.3resigned1",
  "icons": {
    "32": "icons/update.png",
    "64": "icons/update64.png"
  },
  "background": {
    "page": "background.html"
  },
  "options_ui": {
    "page": "options.html"
  },
  "permissions": [
    "activeTab",
    "storage"
  ],
  "browser_action": {
    "default_icon": {
      "32": "icons/update.png"
    }
  },
  "default_locale": "en",
  "browser_specific_settings": {
    "gecko": {
      "id": "{0e797091-a410-4546-91e8-65ea1c0419ad}"
    }
  }
}