Examine source code of YouTube Design Preserver

{
  "applications": {
    "gecko": {
      "id": "{5b7175f9-183b-4421-b105-82ef7ef426d0}",
      "strict_min_version": "48.0"
    }
  },
  "manifest_version": 2,
  "name": "YouTube Design Preserver",
  "version": "2.4.0",
  "description": "__MSG_extDesc__",
  "default_locale": "en",
  "icons": {
    "48": "icons/icon48.png",
    "64": "icons/icon64.png",
    "96": "icons/icon96.png",
    "128": "icons/icon128.png"
  },
  "background": {
    "scripts": [
      "lib/babel-polyfill.min.js",
      "lib/cookie.js",
      "lib/common.js",
      "shared.js",
      "bgscript.js"
    ]
  },
  "permissions": [
    "*://youtube.com/*",
    "*://www.youtube.com/*",
    "cookies",
    "webRequestBlocking",
    "webRequest",
    "storage"
  ],
  "browser_action": {
    "default_icon": {
      "48": "icons/icon48.png",
      "64": "icons/icon64.png",
      "96": "icons/icon96.png",
      "128": "icons/icon128.png"
    },
    "default_popup": "settings/settings.html"
  },
  "options_ui": {
    "page": "settings/settings.html"
  }
}