Examine source code of HideVideo

{
  "manifest_version": 2,
  "name": "HideVideo",
  "version": "1.2",
  "description": "Hides the visuals of a Youtube video.",
  "icons": {
    "48": "icons/border-48.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.youtube.com/*"
      ],
      "js": [
        "hidevideo.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{af5b07a2-159c-4df5-8be8-9b328f0af27d}"
    }
  }
}