Examine source code of PowerKeys

{
  "name": "PowerKeys",
  "version": "1.3",
  "manifest_version": 2,
  "description": "Advanced tools for candykeys.com!",
  "permissions": [
    "storage",
    "*://candykeys.com/*",
    "https://api.coinbase.com/"
  ],
  "background": {
    "scripts": [
      "install.js"
    ]
  },
  "browser_action": {
    "default_icon": "icon.png",
    "default_popup": "popup/popup.html"
  },
  "content_scripts": [
    {
      "matches": [
        "*://candykeys.com/*"
      ],
      "js": [
        "powerkeys.js"
      ]
    }
  ],
  "web_accessible_resources": [
    "dark.css"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{8252bd0c-9e06-4716-ba76-f2ed7d349660}"
    }
  }
}