Examine source code of DateTime Viewer

{
  "manifest_version": 2,
  "name": "DateTime Viewer",
  "version": "1.0",
  "description": "Quickly view the current date and time.",
  "browser_action": {
    "default_icon": "icons/clock-48.png",
    "default_popup": "popup.html",
    "default_title": "Date & Time"
  },
  "icons": {
    "48": "icons/clock-48.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{77a3cef0-8a70-4f97-919b-098bca756dae}"
    }
  }
}