Examine source code of Current Time Popup

{
  "manifest_version": 2,
  "name": "Current Time Popup",
  "version": "1.0",
  "description": "Show the current local time in a popup window.",
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": "icon.png",
    "default_title": "Current Time"
  },
  "permissions": [],
  "icons": {
    "48": "icon.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{f32ab596-284f-4b60-9d16-868142f075a9}"
    }
  }
}