Examine source code of Custom User Agent V2

{
  "manifest_version": 2,
  "name": "Custom User Agent V2",
  "version": "1.2",
  "description": "Thay đổi User-Agent theo website hoặc toàn cục.",
  "permissions": [
    "storage",
    "webRequest",
    "webRequestBlocking",
    "<all_urls>"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "action": {
    "default_popup": "popup.html",
    "default_icon": {
      "64": "icons/logo_64.png"
    }
  },
  "icons": {
    "64": "icons/logo_64.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{63618675-38c6-40fd-815a-85921cea6c26}"
    }
  }
}