Examine source code of Youtube Shadowing

{
  "manifest_version": 2,
  "name": "YtShadow",
  "version": "0.2.4",
  "description": "Shadowing extensions for youtube",
  "icons": {
    "24": "icons/yt-24.png",
    "48": "icons/yt-48.png",
    "96": "icons/yt-96.png"
  },
  "background": {
    "scripts": [
      "browser-polyfill.min.js",
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.youtube.com/*"
      ],
      "js": [
        "browser-polyfill.min.js",
        "yt-shadow.js"
      ],
      "css": [
        "css/yt-blueprint.css"
      ]
    }
  ],
  "browser_action": {
    "browser_style": true,
    "default_icon": {
      "24": "icons/yt-24.png",
      "48": "icons/yt-48.png",
      "96": "icons/yt-96.png"
    },
    "default_title": "Yt Shadow",
    "default_popup": "popup/popup.html"
  },
  "permissions": [
    "*://video.google.com/*",
    "notifications",
    "storage",
    "tabs",
    "unlimitedStorage"
  ]
}