Examine source code of Simple Tiny Timer

{
  "manifest_version": 2,
  "name": "Timer",
  "version": "1.0",
  "icons": {
    "24": "timer_icon_24x24.png",
    "32": "timer_icon_32x32.png",
    "48": "timer_icon_48x48.png"
  },
  "browser_action": {
    "default_popup": "index.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{1d167979-5f4a-4cb2-b960-8d006790f296}"
    }
  }
}