Examine source code of Darker Scrollbars

{
  "name": "Darker Scrollbars",
  "short_name": "DarkerScrollbars",
  "description": "Make the scrollbar darker in Firefox.",
  "version": "1.0.0",
  "manifest_version": 2,
  "icons": {
    "16": "images/icon-16.png",
    "19": "images/icon-19.png",
    "38": "images/icon-38.png",
    "48": "images/icon-48.png",
    "96": "images/icon-96.png",
    "128": "images/icon-128.png"
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "css": [
        "darkscrollbars.css"
      ]
    }
  ],
  "permissions": [
    "activeTab"
  ]
}