chromium/chrome/test/data/extensions/ui/browser_action_popup/manifest.json

{
  "name": "Browser Action Popup",
  "description": "An extension with a popup that sends a message on opening",
  "manifest_version": 2,
  "version": "0.1",
  "browser_action": {
    "default_popup": "popup.html"
  },
  "homepage_url": "https://www.google.com/"
}