Examine source code of sub-shuffler

{
  "manifest_version": 2,
  "name": "Sub-Shuffler",
  "version": "1.2",
  "description": "Opens a random video from your YouTube subscriptions.",
  "icons": {
    "192": "shuffle.jpg"
  },
  "permissions": [
    "identity",
    "activeTab",
    "*://www.youtube.com/*"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "page_action": {
    "default_icon": "shuffle.jpg",
    "default_title": "Open Random Video"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{e12501f2-8bc7-408d-9646-0f4002d6b4f2}"
    }
  }
}