Examine source code of Roll-Block

{
  "manifest_version": 2,
  "name": "RollBlock",
  "version": "1.0",
  "description": "Blocks attempts at rickrolls.",
  "icons": {
    "48": "icons/rick-48.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.youtube.com/watch?v=dQw4w9WgXcQ*"
      ],
      "js": [
        "rollblock.js"
      ]
    }
  ]
}