Examine source code of Video Speed Wheel

{
  "manifest_version": 2,
  "name": "Video Speed Wheel",
  "version": "0.1.0",
  "description": "Adjust video playback speed by mouse wheel.",
  "icons": {
    "48": "icons/icon-48.png",
    "96": "icons/icon-96.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "video-speed-wheel@example.org",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_idle"
    }
  ],
  "permissions": []
}