Examine source code of iCloud Button

{
  "manifest_version": 2,
  "name": "iCloud Button",
  "version": "4.0",
  "description": "Main applications from iCloud.",
  "icons": {
    "128": "icon.png"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ]
    }
  ],
  "background_scripts": [
    {
      "js": [
        "functions.js"
      ]
    }
  ],
  "permissions": [
    "tabs",
    "http://*/*",
    "https://*/*"
  ],
  "browser_action": {
    "default_title": "iCloud Button",
    "default_icon": "icon.png",
    "default_popup": "background.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{c4116147-781a-4c57-955a-e1fb3c376255}"
    }
  }
}