Examine source code of Dark Scroll

{
  "manifest_version": 2,
  "name": "Dark Scroll",
  "version": "1.0",
  "description": "Turn Scrollbar Dark",
  "content_scripts": [
    {
      "matches": [
        "*://*/*"
      ],
      "css": [
        "style.css"
      ]
    }
  ]
}