Examine source code of YouTube Blue Progress Bar

{
  "manifest_version": 2,
  "name": "YouTube Blue Progress Bar",
  "version": "1.0",
  "description": "Blue progress bar for YouTube",
  "browser_specific_settings": {
    "gecko": {
      "data_collection_permissions": {
        "required": [
          "none"
        ],
        "optional": []
      },
      "id": "{464479da-a263-4d27-bd2e-d50c4b0eeaba}"
    }
  },
  "content_scripts": [
    {
      "matches": [
        "*://www.youtube.com/*"
      ],
      "js": [
        "content.js"
      ],
      "css": [
        "styles.css"
      ],
      "run_at": "document_idle"
    }
  ]
}