Examine source code of wYoutubeFocus

{
  "manifest_version": 2,
  "name": "YoutubeFocus",
  "version": "0.1",
  "description": "Убирает все лишнее с сайта Youtube",
  "icons": {
    "48": "icons/ico-48.png"
  },
  "applications": {
    "gecko": {
      "id": "YoutubeFocus@w1575.ru",
      "strict_min_version": "45.0"
    }
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.youtube.com/*"
      ],
      "js": [
        "youtube-focus.js"
      ]
    }
  ]
}