Examine source code of Font Switcher

{
  "manifest_version": 2,
  "name": "Font Switcher",
  "version": "1.0",
  "description": "Easily switch the font of any webpage.",
  "permissions": [
    "activeTab"
  ],
  "browser_action": {
    "default_icon": "icons/font-switcher-48.png",
    "default_popup": "popup.html",
    "default_title": "Switch Font"
  },
  "icons": {
    "48": "icons/font-switcher-48.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{77f1eb84-3d4d-413b-8d45-e50df8dac0ea}"
    }
  }
}