Examine source code of Youtube Master

{
  "name": "Youtube Master",
  "description": "Enhance your user experience on Youtube",
  "version": "1.14",
  "manifest_version": 2,
  "permissions": [
    "https://www.youtube.com/",
    "storage",
    "downloads"
  ],
  "content_scripts": [
    {
      "matches": [
        "https://*.youtube.com/*"
      ],
      "css": [
        "youtube.css",
        "firefox.css"
      ],
      "js": [
        "util.js",
        "constants.js",
        "topbar.js",
        "sort.js",
        "lightsoff.js",
        "speedcontrol.js",
        "screenshot.js",
        "toggle.js",
        "download.js",
        "youtube.js"
      ]
    }
  ],
  "browser_action": {
    "default_popup": "popup.html"
  },
  "content_security_policy": "script-src 'self'; object-src 'self'",
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "icons": {
    "16": "images/icon16.png",
    "48": "images/icon48.png",
    "128": "images/icon128.png"
  },
  "web_accessible_resources": [
    "resources/*"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{6c4567fe-f2e1-4541-a1cf-75e9b84f1cee}"
    }
  }
}