Examine source code of Hidden Zilla

{
  "manifest_version": 2,
  "name": "User Agent Switcher",
  "version": "1.0",
  "description": "Switches User Agent between Chrome and default",
  "permissions": [
    "webRequest",
    "webRequestBlocking",
    "<all_urls>"
  ],
  "browser_action": {
    "default_icon": "icon.png",
    "default_popup": "popup.html"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{8bb45f93-7c6b-41ef-a864-76cdbcf3c58a}"
    }
  }
}