Examine source code of Hamburguesa Background

{
  "manifest_version": 2,
  "name": "Hamburguesa Background",
  "version": "1.0",
  "description": "Adds a gray background to hamburguesa.net",
  "permissions": [
    "tabs",
    "http://hamburguesa.net/"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{18642b0e-27c6-4891-8956-ffaad49b519f}"
    }
  }
}