Examine source code of KJ Eraser

{
  "manifest_version": 2,
  "name": "KJ Eraser",
  "short_name": "KJ Eraser",
  "version": "2.0.0.2",
  "author": "Precious Days Inc.",
  "description": "Erase specified users in the blacklist",
  "page_action": {
    "default_icon": "icon_128.png",
    "default_title": "KJ Eraser Settings",
    "default_popup": "setting.htm"
  },
  "background": {
    "scripts": [
      "js/jquery.min.js",
      "js/common.js",
      "js/background.js"
    ],
    "persistent": false
  },
  "content_scripts": [
    {
      "matches": [
        "*://www.kjclub.com/*"
      ],
      "js": [
        "js/jquery.min.js",
        "js/jquery.fakecrop.js",
        "js/common.js",
        "js/content_scripts.js"
      ],
      "run_at": "document_end"
    }
  ],
  "permissions": [
    "contextMenus",
    "tabs",
    "storage",
    "*://www.kjclub.com/*"
  ],
  "applications": {
    "gecko": {
      "id": "{39e1f1e0-d752-445e-b869-e2b339f82390}"
    }
  },
  "icons": {
    "16": "icon_16.png",
    "48": "icon_48.png",
    "128": "icon_128.png"
  },
  "web_accessible_resources": [
    "cache/board.js"
  ]
}