Examine source code of Google Promo Remover

{
  "manifest_version": 2,
  "name": "Google Promo Remover",
  "version": "1.1",
  "description": "Removes promotional messages from Google",
  "browser_specific_settings": {
    "gecko": {
      "id": "gmail-promo-remover@example.com",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "icons": {
    "72": "icon.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.google.com/*"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_end"
    }
  ],
  "permissions": []
}