Examine source code of Simple Analog Clock

{
  "version": "1.0",
  "manifest_version": 2,
  "name": "Simple Clock",
  "description": "Show popup analog clock.",
  "browser_action": {
    "browser_style": true,
    "default_title": "Clock",
    "default_popup": "clock.html",
    "default_icon": {
      "64": "icons/clock-64.png"
    }
  },
  "icons": {
    "64": "icons/clock-64.png"
  }
}