Examine source code of CssMaster

{
  "manifest_version": 2,
  "name": "CssMaster",
  "version": "1.0",
  "description": "Allows for basic CSS manipulation of elements with simple hotkeys",
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "CssMaster.js"
      ]
    }
  ]
}