Examine source code of Speed Manager

{
  "manifest_version": 2,
  "name": "Speed Manager",
  "description": "This control the speed of youtube videos upto 10x",
  "version": "1.0.0",
  "icons": {
    "16": "icon_16.png",
    "48": "icon_48.png",
    "128": "icon_128.png"
  },
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "page_action": {
    "default_icon": "icon.png",
    "default_popup": "popup.html"
  },
  "content_scripts": [
    {
      "matches": [
        "https://www.youtube.com/watch*"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "permissions": [
    "activeTab",
    "tabs",
    "storage",
    "declarativeContent",
    "*://www.youtube.com/watch*"
  ]
}