Examine source code of Custom Search

{
  "manifest_version": 2,
  "name": "Custom Search",
  "version": "1.0",
  "description": "Search from your browser with your preferred search engine.",
  "permissions": [
    "tabs"
  ],
  "browser_action": {
    "default_icon": "icons/search-48.png",
    "default_popup": "popup.html",
    "default_title": "Custom Search"
  },
  "icons": {
    "48": "icons/search-48.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{08766e04-cc49-40f4-b271-413b68d689a4}"
    }
  }
}