chrome/test/data/extensions/platform_apps/app_icon/manifest.json

{
  "name": "Platform App Test: app icon test",
  "manifest_version": 2,
  "version": "1",
  "app": {
    "background": {
      "scripts": ["test.js"]
    }
  },
  "icons": {
    "48": "icon48.png"
  }
}