chromium/chrome/test/data/extensions/search_provider_override/manifest.json

{
  "name": "Search Override Extension",
  "manifest_version": 2,
  "version": "0.1",
  "description": "A simple extension that overrides the search engine",
  "default_locale": "en",
  "permissions": ["storage"],
  "chrome_settings_overrides": {
    "search_provider": {
      "search_url": "https://www.example.__MSG_url_domain__/?q={searchTerms}",
      "name": "Example",
      "keyword": "word",
      "encoding": "UTF-8",
      "is_default": true,
      "favicon_url": "https://example.com/favicon.ico"
    }
  }
}