Examine source code of Theme Customizer

{
  "manifest_version": 2,
  "name": "Theme Customizer",
  "version": "1.0",
  "description": "Customize the browser theme with a simple background color changer.",
  "icons": {
    "48": "icon.png"
  },
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": "icon.png"
  },
  "permissions": [
    "theme"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{5da23d10-f319-4f88-9cd3-1720075e76b5}"
    }
  }
}