Examine source code of Direct Link

{
  "manifest_version": 2,
  "name": "Direct Link",
  "version": "0.0.1resigned1",
  "applications": {
    "gecko": {
      "id": "direct-link@nekoziroo.org"
    }
  },
  "default_locale": "ja",
  "description": "__MSG_extensionDescription__",
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "permissions": [
    "webRequest",
    "webRequestBlocking",
    "*://jump.5ch.net/*"
  ]
}