Examine source code of BetterYTV

{
  "name": "BetterYTV",
  "manifest_version": 2,
  "version": "1.0.1",
  "content_scripts": [
    {
      "matches": [
        "*://www.youtube.com/*",
        "*://youtube.com/*"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "page_action": {
    "default_icon": "icon.png"
  },
  "permissions": [
    "https://api.twitch.tv/kraken/users",
    "https://api.betterttv.net/*",
    "https://www.youtube.com/*"
  ],
  "icons": {
    "192": "icon.png"
  }
}