Examine source code of Classy

{
  "manifest_version": 2,
  "name": "Classy",
  "version": "1.1resigned1",
  "description": "Enumerates all the classes applied to an HTML page.",
  "icons": {
    "48": "classy-icon.png"
  },
  "permissions": [
    "tabs"
  ],
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "enumerateClassNames.js"
      ]
    }
  ],
  "sidebar_action": {
    "default_title": "Classy",
    "default_panel": "sidebar.html",
    "default_icon": "icons/border-48.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{c6c25a5d-2991-489c-a8a3-0937b43e1d89}"
    }
  }
}