Examine source code of BarbBlock

{
  "manifest_version": 2,
  "name": "BarbBlock",
  "description": "Blocks requests to sites which have used legal threats to remove themselves from other blacklists.",
  "version": "1.5",
  "icons": {
    "16": "icon/icon16.png",
    "32": "icon/icon32.png",
    "48": "icon/icon48.png",
    "128": "icon/icon128.png"
  },
  "background": {
    "scripts": [
      "barbblock.js"
    ]
  },
  "permissions": [
    "webRequest",
    "webRequestBlocking",
    "<all_urls>"
  ]
}