Examine source code of read CSS rule values

{
  "manifest_version": 2,
  "name": "read CSS rule values",
  "version": "1.0",
  "description": "DOM (Document Object Model) object can read and manipulate CSS rules. We can use the following approaches to read all the Embedded CSS rules using JavaScript. ",
  "permissions": [],
  "browser_action": {
    "default_popup": "game.html",
    "default_icon": {
      "128": "images/css-logo.png"
    }
  },
  "icons": {
    "128": "images/css-logo.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{9fd10f4d-0903-4eaa-872b-05aab8a74b37}"
    }
  }
}