Examine source code of SlimJim

{
  "manifest_version": 2,
  "name": "SlimJim",
  "version": "1.1",
  "description": "You love a slim scrollbar. Don't you?",
  "icons": {
    "64": "icons/scroll.png"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "css.js"
      ]
    }
  ]
}