Examine source code of YoutubeUtils(YU)

{
  "manifest_version": 2,
  "name": "YoutubeUtils",
  "version": "2.2.0",
  "description": "Turn off/on control menu; increase/decrease video speed",
  "content_scripts": [
    {
      "matches": [
        "*://*.youtube.com/*"
      ],
      "js": [
        "src/script.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{6702f09e-8ab9-4733-b1e0-0d505818e1de}"
    }
  }
}