chromium/chrome/test/data/extensions/manifest_tests/platforms_key.json

{
  "name": "platforms key does not cause a warning",
  "version": "1",
  "manifest_version": 3,
  "platforms": [
    {
      "os": "win",
      "arch": "x86",
      "sub_package_path": "_platform_specific/win_x86_anyname/"
    }
  ]
}