Examine source code of Facebook pleasant theme

{
  "manifest_version": 2,
  "name": "fb pleasant theme",
  "version": "2.0",
  "description": "changes the appearance of facebook to a more friendly theme.",
  "icons": {
    "48": "img.png",
    "96": "img.png"
  },
  "web_accessible_resources": [
    "first.png"
  ],
  "content_scripts": [
    {
      "matches": [
        "*://*.facebook.com/*"
      ],
      "css": [
        "z.css"
      ]
    }
  ]
}