Examine source code of Youtube controler

{
  "manifest_version": 2,
  "name": "Youtube controler",
  "version": "0.1",
  "description": "Control an existing youtube tab by this remote",
  "homepage_url": "https://github.com/thibsc/youtube-remote",
  "icons": {
    "48": "assets/icons/play-button.png"
  },
  "permissions": [
    "*://www.youtube.com/*",
    "tabs"
  ],
  "browser_action": {
    "default_icon": "assets/icons/play-button.png",
    "default_title": "Youtube remote",
    "default_popup": "src/youtube_remote.html"
  },
  "web_accessible_resources": [
    "assets/js/youtube_getter.js"
  ]
}