Examine source code of World Clock Viewer

{
  "manifest_version": 2,
  "name": "World Clock Viewer",
  "version": "1.2",
  "description": "Customizable World clock app.",
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": "icon.png"
  },
  "icons": {
    "48": "icon.png"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "permissions": [
    "storage"
  ],
  "options_ui": {
    "page": "options.html",
    "open_in_tab": true
  },
  "applications": {
    "gecko": {
      "id": "worldclock@gamesome.com"
    }
  }
}