chromium/chrome/test/data/extensions/platform_apps/ephemeral_apps/filesystem_retain_entries/manifest.json

{
  "name": "Ephemeral Apps Retain File Entries",
  "version": "1.0",
  "manifest_version": 2,
  "app": {
    "background": {
      "scripts": ["main.js"]
    }
  },
  "permissions": ["storage", {"fileSystem": ["write", "retainEntries"]}]
}