Examine source code of Auto Page Reloader is

{
  "manifest_version": 2,
  "name": "Auto Page Reloader",
  "version": "1.0",
  "description": "Automatically reload the current page at custom intervals.",
  "permissions": [
    "tabs",
    "activeTab"
  ],
  "browser_action": {
    "default_icon": {
      "16": "icon.png"
    },
    "default_popup": "popup.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{7e38b87b-5286-4b60-b909-256b05673f70}"
    }
  }
}