Examine source code of Youtube Page Embed

{
  "manifest_version": 2,
  "name": "Modify Embed",
  "version": "1.0",
  "permissions": [
    "activeTab",
    "contextMenus"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{a3161fb2-eeb6-40c8-adb0-0495c1dc4ae9}"
    }
  }
}