Examine source code of Localhost Navigator

{
  "manifest_version": 2,
  "name": "Localhost Navigator",
  "version": "1.0",
  "description": "Quickly navigate to different localhost ports without using the mouse.",
  "icons": {
    "48": "icon.png"
  },
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": "icon.png"
  },
  "permissions": [
    "activeTab"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{4b846c1a-52ad-4334-beec-3840c696d157}"
    }
  }
}