Examine source code of CDADownloadButton

{
  "manifest_version": 2,
  "name": "cdalink",
  "version": "1.0",
  "description": "Dodaje przycisk download zamiast fb share",
  "Author": "Andrzej Połetek",
  "content_scripts": [
    {
      "matches": [
        "*://*.cda.pl/*"
      ],
      "js": [
        "CDADownloadButton.js"
      ]
    }
  ]
}