Examine source code of JustLabelMe

{
  "manifest_version": 2,
  "name": "JustLabelMe",
  "version": "1.4.2resigned1",
  "icons": {
    "16": "/icons/icon16.png",
    "24": "/icons/icon24.png",
    "36": "/icons/icon32.png",
    "64": "/icons/icon64.png",
    "128": "/icons/icon128.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://www.amazon.com/*",
        "*://just-label.me/*",
        "file:///*"
      ],
      "css": [
        "/css/main.css"
      ],
      "js": [
        "/js/main.js"
      ]
    }
  ],
  "background": {
    "scripts": [
      "/js/background.js"
    ]
  },
  "browser_action": {
    "default_title": "JustLabelMe",
    "default_icon": "/icons/icon32.png"
  },
  "permissions": [
    "<all_urls>",
    "*://www.amazon.com/*",
    "file:///*",
    "*://just-label.me/*",
    "activeTab",
    "tabs",
    "storage"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{f03614c1-ecc0-4ffd-8b70-1845ef878fe8}"
    }
  }
}