Examine source code of Close All Windows

{
  "manifest_version": 2,
  "name": "Close All Windows",
  "version": "1.1resigned1",
  "description": "Close all Firefox windows when a configurable keyboard shortcut is pressed",
  "commands": {
    "quit_command": {
      "suggested_key": {
        "default": "Ctrl+Comma"
      }
    }
  },
  "background": {
    "scripts": [
      "quit_daemon.js"
    ]
  },
  "browser_action": {
    "browser_style": true,
    "default_icon": "icon/quit.svg",
    "default_popup": "settings/index.html",
    "default_title": "Configure Quit Shortcut"
  },
  "icons": {
    "48": "icon/quit.svg",
    "96": "icon/quit.svg"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{6f92a9a3-fbee-4caf-96df-36060f2c6b3d}"
    }
  }
}