Examine source code of Toolbox icon

{
  "manifest_version": 2,
  "name": "Toolbox icon",
  "version": "1.0",
  "description": "The toolbox icon is typically designed to represent a collection of tools that aid in repair, maintenance, or setup – both in physical (mechanical, electrical) and digital (software, apps) contexts.",
  "icons": {
    "48": "icon.png"
  },
  "browser_action": {
    "default_icon": "icon.png",
    "default_popup": "popup.html",
    "default_title": "Click me!"
  },
  "permissions": [
    "activeTab"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{7909cbcd-9905-4629-a55d-93cbc888d3c1}"
    }
  }
}