Examine source code of SisRastreio

{
  "manifest_version": 2,
  "name": "SisRastreio",
  "version": "0.0.3resigned1",
  "description": "Abre a página de rastreamento dos Correios!",
  "icons": {
    "48": "icon48.png",
    "128": "icon128.png"
  },
  "page_action": {
    "default_icon": {
      "19": "icon19.png",
      "38": "icon38.png",
      "48": "icon48.png",
      "128": "icon128.png"
    },
    "default_title": "Sisbot"
  },
  "author": "http://www.sispostag.com.br/",
  "permissions": [
    "tabs",
    "declarativeContent"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "content_scripts": [
    {
      "js": [
        "inject/jquery.js",
        "inject/sisrastreio.js"
      ],
      "matches": [
        "http://*.correios.com.br/sistemas/rastreamento/*"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "@sisrastreiofx"
    }
  }
}