Examine source code of Percent Scrollbar

{
  "manifest_version": 2,
  "name": "Percent Scrollbar",
  "version": "0.2.0",
  "description": "Replaces the main vertical scrollbar with text showing percent scrolled",
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "lib.js",
        "content_scripts/percent-scrollbar.js"
      ],
      "css": [
        "content_scripts/percent-scrollbar.css"
      ],
      "run_at": "document_end"
    }
  ],
  "background": {
    "scripts": [
      "lib.js",
      "background.js"
    ]
  },
  "browser_action": {
    "default_icon": "icons/percent-scrollbar-96.png",
    "default_title": "Percent Scrollbar",
    "default_popup": "popup/popup.html"
  },
  "options_ui": {
    "page": "options/options.html"
  },
  "icons": {
    "96": "icons/percent-scrollbar-96.png"
  },
  "permissions": [
    "storage",
    "activeTab"
  ]
}