Examine source code of Maintenance icon

{
  "manifest_version": 2,
  "name": "Maintenance icon",
  "version": "1.0",
  "description": "The maintenance icon usually means that the system is being repaired, upgraded or checked.",
  "icons": {
    "48": "icon.png"
  },
  "browser_action": {
    "default_icon": "icon.png",
    "default_popup": "popup.html",
    "default_title": "Click me!"
  },
  "permissions": [
    "activeTab"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{b88f44f6-f148-45eb-b9f0-696fa72c117d}"
    }
  }
}